refactor: optional last tab page

[flxzt]

ground work to continue progress on #1196

[anesthetice]

There's a weird issue when opening files:

issue.mp4

(rnote:93079): Gtk-WARNING **: 12:32:08.994: Unknown key gtk-modules in /home/oether/.config/gtk-4.0/settings.ini

(rnote:93079): Adwaita-WARNING **: 12:32:09.007: Using GtkSettings:gtk-application-prefer-dark-theme with libadwaita is unsupported. Please use AdwStyleManager:color-scheme instead.

(rnote:93079): Gtk-WARNING **: 12:32:09.199: Creating a portal monitor failed: GDBus.Error:org.freedesktop.DBus.Error.UnknownMethod: No such interface “org.freedesktop.portal.Inhibit” on object at path /org/freedesktop/portal/desktop

(rnote:93079): Adwaita-CRITICAL **: 12:32:09.280: adw_tab_view_append: assertion 'gtk_widget_get_parent (child) == NULL' failed
thread 'main' panicked at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/libadwaita-0.7.0/src/auto/tab_page.rs:14:1:
assertion failed: !ptr.is_null()
stack backtrace:
   0:     0x55a0a87143d5 - std::backtrace_rs::backtrace::libunwind::trace::h58eed11393533053
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/../../backtrace/src/backtrace/libunwind.rs:116:5
   1:     0x55a0a87143d5 - std::backtrace_rs::backtrace::trace_unsynchronized::h6af9bae28ebb6388
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x55a0a87143d5 - std::sys_common::backtrace::_print_fmt::hb6748916642a4fb2
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x55a0a87143d5 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h3692694645b1bb6a
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x55a0a87404ab - core::fmt::rt::Argument::fmt::h7aa93977ba74ae0f
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/fmt/rt.rs:165:63
   5:     0x55a0a87404ab - core::fmt::write::h5131d80b4c69b88d
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/fmt/mod.rs:1168:21
   6:     0x55a0a871124f - std::io::Write::write_fmt::h1fb327a7d8b0eb36
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/io/mod.rs:1835:15
   7:     0x55a0a87141ae - std::sys_common::backtrace::_print::he6ebb7b9d89f4456
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x55a0a87141ae - std::sys_common::backtrace::print::h998d75b840f75a73
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x55a0a8715779 - std::panicking::default_hook::{{closure}}::h18ec7fe6a38b9da0
  10:     0x55a0a871551a - std::panicking::default_hook::hfb3f22c2e4075a6a
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:298:9
  11:     0x55a0a8715c13 - std::panicking::rust_panic_with_hook::h51af00bcb4660c4e
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:795:13
  12:     0x55a0a8715abb - std::panicking::begin_panic_handler::{{closure}}::h39f76aa863fbe8ce
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:656:13
  13:     0x55a0a8714899 - std::sys_common::backtrace::__rust_end_short_backtrace::h4d10fc2251b89840
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:171:18
  14:     0x55a0a8715827 - rust_begin_unwind
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:652:5
  15:     0x55a0a7949263 - core::panicking::panic_fmt::h319840fcbcd912ef
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/panicking.rs:72:14
  16:     0x55a0a794930c - core::panicking::panic::h19def44c80243eda
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/panicking.rs:146:5
  17:     0x55a0a7b04903 - <libadwaita::auto::tab_page::TabPage as glib::translate::FromGlibPtrNone<*mut libadwaita_sys::AdwTabPage>>::from_glib_none::h401585966927c157
                               at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/glib-0.20.3/src/object.rs:894:17
  18:     0x55a0a7b04903 - glib::translate::from_glib_none::hd5c37f39192b3eb6
                               at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/glib-0.20.3/src/translate.rs:1626:5
  19:     0x55a0a7b04903 - libadwaita::auto::tab_view::TabView::append::h3db2d30a599e583a
                               at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/libadwaita-0.7.0/src/auto/tab_view.rs:64:13
  20:     0x55a0a7aa556d - rnote::appwindow::RnAppWindow::append_wrapper_new_tab::hd11cfd1f410cf18d
                               at /home/oether/Documents/Rust/rnote/crates/rnote-ui/src/appwindow/mod.rs:347:20
  21:     0x55a0a7a59a0a - rnote::appwindow::RnAppWindow::try_open_file::{{closure}}::h8eba119561cac8dc
                               at /home/oether/Documents/Rust/rnote/crates/rnote-ui/src/appwindow/mod.rs:560:25
  22:     0x55a0a7a59a0a - rnote::appwindow::RnAppWindow::open_file_w_dialogs::{{closure}}::h6c5990d77986b483
                               at /home/oether/Documents/Rust/rnote/crates/rnote-ui/src/appwindow/mod.rs:506:14
  23:     0x55a0a7a521ee - rnote::app::imp::RnApp::new_appwindow_init_show::{{closure}}::h2b6a4dd40ace9b15
                               at /home/oether/Documents/Rust/rnote/crates/rnote-ui/src/app/mod.rs:144:80
  24:     0x55a0a7a521ee - glib::main_context_futures::<impl glib::auto::main_context::MainContext>::spawn_local_with_priority::{{closure}}::hba98d97fdd825521
                               at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/glib-0.20.3/src/main_context_futures.rs:579:24
  25:     0x55a0a86e2701 - <glib::main_context_futures::FutureWrapper as core::future::future::Future>::poll::h127851f35c36832b
  26:     0x55a0a86e2701 - glib::main_context_futures::TaskSource::poll::{{closure}}::{{closure}}::h8f93e36d6bbe8e21
                               at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/glib-0.20.3/src/main_context_futures.rs:248:25
  27:     0x55a0a86e2701 - core::ops::function::FnOnce::call_once::h3f63380551008dee
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/ops/function.rs:250:5
  28:     0x55a0a86e2701 - <core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::hff1fb62145bf2ebf
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/panic/unwind_safe.rs:272:9
  29:     0x55a0a86e2701 - std::panicking::try::do_call::hdd9d7e24d22d0d21
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:559:40
  30:     0x55a0a86e2701 - std::panicking::try::h6ca484884a7e00df
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:523:19
  31:     0x55a0a86e2701 - std::panic::catch_unwind::h67635503d3f4f3e8
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panic.rs:149:14
  32:     0x55a0a86e2701 - glib::main_context_futures::TaskSource::poll::{{closure}}::h5b2e008bbbc6314f
                               at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/glib-0.20.3/src/main_context_futures.rs:247:31
  33:     0x55a0a86e2701 - glib::main_context::<impl glib::auto::main_context::MainContext>::with_thread_default::h3ffcf817cb0e65e5
                               at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/glib-0.20.3/src/main_context.rs:154:12
  34:     0x55a0a86de6a3 - glib::main_context_futures::TaskSource::poll::h64f12e84cf886aaf
                               at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/glib-0.20.3/src/main_context_futures.rs:239:9
  35:     0x55a0a86de6a3 - glib::main_context_futures::TaskSource::dispatch::h34c543a4d77b7034
                               at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/glib-0.20.3/src/main_context_futures.rs:75:34
  36:     0x7d35c40db559 - <unknown>
  37:     0x7d35c413e157 - <unknown>
  38:     0x7d35c40daa55 - g_main_context_iteration
  39:     0x7d35c3dd5c36 - g_application_run
  40:     0x55a0a7bea3fe - gio::application::ApplicationExtManual::run_with_args::h5e17fb1239d207d4
                               at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/gio-0.20.1/src/application.rs:29:13
  41:     0x55a0a7bea3fe - gio::application::ApplicationExtManual::run::h8a8641273274b4bf
                               at /home/oether/Documents/Rust/rnote/_mesonbuild/cargo-home/registry/src/index.crates.io-6f17d22bba15001f/gio-0.20.1/src/application.rs:22:9
  42:     0x55a0a7b81947 - rnote::main::h79096961e922184a
                               at /home/oether/Documents/Rust/rnote/crates/rnote-ui/src/main.rs:86:5
  43:     0x55a0a7b9c303 - core::ops::function::FnOnce::call_once::h000a4e9eef7c4b89
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/ops/function.rs:250:5
  44:     0x55a0a7b9c303 - std::sys_common::backtrace::__rust_begin_short_backtrace::ha375c7dd8aedcf46
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/sys_common/backtrace.rs:155:18
  45:     0x55a0a7ab9b59 - std::rt::lang_start::{{closure}}::hf1ce436be780aff2
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/rt.rs:159:18
  46:     0x55a0a870901d - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::hb84c63630a35bb05
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/core/src/ops/function.rs:284:13
  47:     0x55a0a870901d - std::panicking::try::do_call::h8d62108d97b3e028
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:559:40
  48:     0x55a0a870901d - std::panicking::try::h0c0b9a214b9691f1
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:523:19
  49:     0x55a0a870901d - std::panic::catch_unwind::ha8912f28da143edb
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panic.rs:149:14
  50:     0x55a0a870901d - std::rt::lang_start_internal::{{closure}}::h2baf77487fc7f90d
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/rt.rs:141:48
  51:     0x55a0a870901d - std::panicking::try::do_call::h36fdc82521d3343f
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:559:40
  52:     0x55a0a870901d - std::panicking::try::h58aa1415c41e30ec
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panicking.rs:523:19
  53:     0x55a0a870901d - std::panic::catch_unwind::h3c4b5a8c3b1c4acf
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/panic.rs:149:14
  54:     0x55a0a870901d - std::rt::lang_start_internal::h63a185b0ddd212e9
                               at /rustc/051478957371ee0084a7c0913941d2a8c4757bb9/library/std/src/rt.rs:141:20
  55:     0x55a0a7b81c9c - main
  56:     0x7d35c2b33e08 - <unknown>
  57:     0x7d35c2b33ecc - __libc_start_main
  58:     0x55a0a7949df5 - _start
  59:                0x0 - <unknown>

[flxzt]

@anesthetice thanks for pointing this out. This was a logic error in the try_open_file() function and should be fixed with commit 4e4df93