fix: Pop all events from stack

It can happen that the dialog is not able to render before the next event is received. Before that patch that could have lead to some random dangling events that get shown once the root screen gets rebuild.

This patch puts new events in a last in last out order and on rendering the task dialog pops all events from the queue. This way we prevent having dangling events.

fixes #2506

mobile/lib/common/background_task_change_notifier.dart

@@ -7,7 +7,7 @@ import 'package:get_10101/logger/logger.dart';
 class Stack<E> {
   final _list = <E>[];
 
-  void push(E value) => _list.add(value);
+  void push(E value) => _list.insert(0, value);
 
   E pop() => _list.removeLast();
 

mobile/lib/common/background_task_dialog_screen.dart

@@ -64,7 +64,13 @@ class _BackgroundTaskDialogScreenState extends State<BackgroundTaskDialogScreen>
             pageBuilder: (context, _, __) {
               // watch task updates from within the dialog.
               try {
-                final task = context.watch<BackgroundTaskChangeNotifier>().events.pop();
+                final events = context.watch<BackgroundTaskChangeNotifier>().events;
+                var task = events.pop();
+                while (events.isNotEmpty) {
+                  // we might have received very fast events. In that case we pop until we are at
+                  // the latest event.
+                  task = events.pop();
+                }
                 if (activeTask != null && task.type != activeTask!.type) {
                   logger.w("Received another task event $task while $activeTask is still active!");
                 }