moulti run: fix crash when passing a non-executable script.

CHANGELOG.md

@@ -16,6 +16,7 @@ Although Moulti's Python packages, modules and functions are obviously available
 
 - diff, load, manpage, step delete: improve pipelining so as to prevent deadlocks
 - server-side networking: use non-blocking methods to deal with non-blocking sockets
+- `moulti run path/to/non_executable_script` used to crash
 
 ## [1.28.0] - 2024-12-29
 

src/moulti/app.py

@@ -403,6 +403,8 @@ def exec(self, command: list[str]) -> None:
 		worker = get_current_worker()
 		harvest_output = self.output_policy() # Harvest stdout/stderr lines
 		output_delegated = False
+		output_selector = None
+		process = None
 		try:
 			self.init_command_running = True
 			original_command = command.copy()
@@ -417,7 +419,6 @@ def exec(self, command: list[str]) -> None:
 			process = subprocess.Popen(command, **popen_args, **self.output_policy_popen_args())
 			self.logconsole(f'exec: {command} launched with PID {process.pid}')
 			returncode = None
-			output_selector = None
 			if harvest_output:
 				output_selector = selectors.DefaultSelector()
 				assert process.stdout is not None # for mypy
@@ -451,7 +452,7 @@ def exec(self, command: list[str]) -> None:
 			self.init_command_running = False
 		finally:
 			clean_selector(output_selector, close_fds=False, close=True)
-			if harvest_output and not output_delegated and process.stdout is not None:
+			if harvest_output and not output_delegated and process is not None and process.stdout is not None:
 				self.logconsole(f'exec: no output harvested, closing child process stdout fd {process.stdout.fileno()}')
 				process.stdout.close()