Fix memory leaks when doing "Save & Quit"

Steps to reproduce were:
* Open Blender (no need for factory settings, "Promt Quit" needs to be enabled)
* Edit the file (e.g. translate some object)
* Quit Blender but don't skip quit promt
* Press "Save & Quit"
* Save the file

Not sure if Windows supports the "Save & Quit" behavior, so this may not have
applied to Windows.

source/blender/windowmanager/intern/wm_files.c

@@ -2076,7 +2076,7 @@ static int wm_save_as_mainfile_exec(bContext *C, wmOperator *op)
 	WM_event_add_notifier(C, NC_WM | ND_FILESAVE, NULL);
 
 	if (RNA_boolean_get(op->ptr, "exit")) {
-		WM_exit(C);
+		wm_exit_schedule_delayed(C);
 	}
 
 	return OPERATOR_FINISHED;