Merge pull request #4862 from pangeachat/4855-disabled-learning-tools-popup-can-be-spammed

fix: close previous snackbar before opening new mode disabled snackbar

lib/pangea/toolbar/reading_assistance/select_mode_buttons.dart

@@ -211,6 +211,7 @@ class SelectModeButtonsState extends State<SelectModeButtons> {
   }
 
   Future<void> modeDisabled() async {
+    ScaffoldMessenger.of(context).hideCurrentSnackBar();
     ScaffoldMessenger.of(context).showSnackBar(
       SnackBar(
         content: Text(L10n.of(context).modeDisabled),