TextEditor/GMLPlayground: Don't close app if user aborts save on exit

Author: https://github.com/matthewbjones
Commit: 9720261540
Pull-request: https://github.com/SerenityOS/serenity/pull/7653
Issue: https://github.com/SerenityOS/serenity/issues/7247

Userland/Applications/TextEditor/MainWidget.cpp

@@ -672,6 +672,8 @@ bool MainWidget::request_close()
 
     if (result == GUI::MessageBox::ExecYes) {
         m_save_action->activate();
+        if (editor().document().is_modified())
+            return false;
         return true;
     }