ask for saving modified editor files if octave is closed (bug #38689) * files-editor-tab.cc(constrctor): init new flag indicating if app is closing, (check_file_modified): message box is modal if app is closing, no cancel, parent of box is the editor's tab widget for a correct palcement of the box, (conditional_close): new second arg: flag for closing app (default false), it is stored in the tab's class wide flag * file-editor-tab.h: second arg for conditional_close and new class wide flag * file-editor.cc(destructor): sending close requests to all editor tabs with flag indicating the application is closing (add_file_editor_tab): new arg for fetab_close_request and conditional_close * file-editor.h: new 2nd arg for fetab_close_request (closing app, def. false) * main-window.cc(destructor): delete editor window first for showing the message boxes for modified editor files in front of a complete gui

--- a/libgui/src/m-editor/file-editor-tab.h
+++ b/libgui/src/m-editor/file-editor-tab.h
@@ -55,7 +55,7 @@
   void notice_settings (const QSettings *settings);
 
   // Will initiate close if associated with the identifier tag.
-  void conditional_close (const QWidget *ID);
+  void conditional_close (const QWidget *ID, bool app_closing = false);
 
   // Change to a different editor tab by identifier tag.
   void change_editor_state (const QWidget *ID);
@@ -182,6 +182,7 @@
 
   bool _long_title;
   bool _copy_available;
+  bool _app_closing;
 
   QFileSystemWatcher _file_system_watcher;