amend 365e3ef8e2 to be "more right"

NoteBase-derived note objects must delete their children, because
often they are deleted long before the parent (group) is. However,
in MidiView::clear_events() we used to call _note_group->clear (true)
first, which would delete the canvas items owned by these objects,
without them knowing about it. This made it dangerous for them
to delete those same items in their destructors.

This reverses the ordering so that NoteBase objects are deleted first
(along with their canvas items) and after that we clear _note_group
which will address any danging canvas items created there that are
not owned by a NoteBase-derived object

gtk2_ardour/hit.cc

@@ -40,9 +40,7 @@ Hit::Hit (MidiView& region, Item* parent, double size, const std::shared_ptr<Not
 
 Hit::~Hit ()
 {
-	/* do not delete the visual note here, because that will be handled by
-	 * the parent
-	 */
+	delete _polygon;
 }
 
 void

gtk2_ardour/midi_view.cc

@@ -876,12 +876,13 @@ MidiView::clear_events ()
 	// clear selection without signaling or trying to change state of event objects
 	_selection.clear ();
 	clear_ghost_events ();
-	/* This will delete all the _visual_note members of the NoteBase* elements in the _events map */
-	_note_group->clear (true);
-	/* The above did not actually delete the the NoteBase* elements, so do that now  */
 	for (auto & [model_note,gui_note] : _events) {
 		delete gui_note;
 	}
+	/* This will delete any danging canvas items that were not owned by the
+	 * NoteBase objects we just deleted.
+	 */
+	_note_group->clear (true);
 	_events.clear();
 	_patch_changes.clear();
 	_sys_exes.clear();

gtk2_ardour/note.cc

@@ -39,9 +39,7 @@ Note::Note (MidiView& region, ArdourCanvas::Item* parent, const std::shared_ptr<
 
 Note::~Note ()
 {
-	/* do not delete the canvas item here, because that will be handled by
-	 * the parent
-	 */
+	delete _visual_note;
 }
 
 void

gtk2_ardour/note_base.cc

@@ -88,7 +88,7 @@ NoteBase::NoteBase(MidiView& v, bool with_events, const std::shared_ptr<NoteType
 NoteBase::~NoteBase()
 {
 	_view.note_deleted (this);
-	/* do not delete _text, parent will do so */
+	delete _text;
 }
 
 void