Fix issue with building "Bookmarks" menu

When building the "Bookmarks" menu, the items under the "Bookmarks Menu"
folder are inserted first, followed by the items in the "Other
Bookmarks" folder. A nextMenuId field is used to keep track of the next
available menu item ID.

Previously, that field wasn't being initialized, which meant that if
there were no "Bookmarks Menu" items, the field would never be set. When
inserting the "Other Bookmarks" items, the uninitialized field would be
used. Depending on the exact value of the field, no items might be added
(if the value was above the assigned range), or items might be added,
but not respond correctly when selected.

To fix this, the nextMenuId field is now initialized when building the
menu.

Documentation/User/History.txt

@@ -131,6 +131,9 @@ Bug fixes:
   appear on the bookmarks toolbar, if the toolbar was initially
   empty. The height of the toolbar is now updated when an item is
   added, which fixes this issue.
+- If the only bookmarks that appeared in the "Bookmarks" menu
+  were under the "Other Bookmarks" folder, the menu wouldn't be
+  built correctly.
 - Fixed an issue with handling the properties item on the
   background context menu.
 - Previously, listview groups were always sorted by name. Now,

Explorer++/Explorer++/Bookmarks/UI/BookmarksMainMenu.cpp

@@ -52,6 +52,7 @@ void BookmarksMainMenu::OnMainMenuPreShow(HMENU mainMenu)
 {
 	std::vector<wil::unique_hbitmap> menuImages;
 	BookmarkMenuBuilder::MenuInfo menuInfo;
+	menuInfo.nextMenuId = m_menuIdRange.startId;
 	auto bookmarksMenu = BuildMainBookmarksMenu(menuImages, menuInfo);
 
 	MENUITEMINFO mii;