fix crash when switching tasks while saving, should fix https://github.com/PhilippC/keepass2android/issues/719

src/Kp2aBusinessLogic/database/edit/ActionOnFinish.cs

@@ -36,8 +36,11 @@ namespace keepass2android
 		{
 			_actionToPerform = actionToPerform;
 		}
-        
-		public override void Run()
+
+		//if set to true, the previously active active will be passed to ActionToPerformOnFinish instead null if no activity is on foreground
+        public bool AllowInactiveActivity { get; set; }
+
+        public override void Run()
 		{
 			if (Message == null)
 				Message = "";
@@ -46,7 +49,7 @@ namespace keepass2android
 				Handler.Post(() => {_actionToPerform(Success, Message, ActiveActivity);});
 			}
 			else
-				_actionToPerform(Success, Message, ActiveActivity);
+				_actionToPerform(Success, Message, AllowInactiveActivity ? (ActiveActivity ?? PreviouslyActiveActivity) :  ActiveActivity);
 			base.Run();
 		}
 	}

src/Kp2aBusinessLogic/database/edit/OnFinish.cs

@@ -39,7 +39,7 @@ namespace keepass2android
         protected OnFinish BaseOnFinish;
 		protected Handler Handler;
 		private ProgressDialogStatusLogger _statusLogger = new ProgressDialogStatusLogger(); //default: no logging but not null -> can be used whenever desired
-	    private Activity _activeActivity;
+	    private Activity _activeActivity, _previouslyActiveActivity;
 
 
 	    public ProgressDialogStatusLogger StatusLogger
@@ -53,7 +53,12 @@ namespace keepass2android
 	        get { return _activeActivity; }
 	        set
 	        {
-	            _activeActivity = value;
+                if (_activeActivity != null && _activeActivity != _previouslyActiveActivity)
+                {
+                    _previouslyActiveActivity = _activeActivity;
+
+                }
+				_activeActivity = value;
 	            if (BaseOnFinish != null)
 	            {
 	                BaseOnFinish.ActiveActivity = value;
@@ -61,8 +66,15 @@ namespace keepass2android
 	        }
 	    }
 
+        public Activity PreviouslyActiveActivity
+        {
+            get { return _previouslyActiveActivity; }
 
-	    protected OnFinish(Activity activeActivity, Handler handler)
+        }
+
+
+
+		protected OnFinish(Activity activeActivity, Handler handler)
 	    {
 	        ActiveActivity = activeActivity;
 			BaseOnFinish = null;