diff --git a/ChatController/ChatMainControl.xaml.cs b/ChatController/ChatMainControl.xaml.cs
index 7068509..f7a4694 100644
--- a/ChatController/ChatMainControl.xaml.cs
+++ b/ChatController/ChatMainControl.xaml.cs
@@ -322,64 +322,83 @@ namespace ChatController
 
         private void SelectContact(Contact pContact)
         {
-            if(pContact == null)
+            try
             {
-                return;
-            }
-
-            ShouldInterruptContactsThread = true;
-
-            StartWaitingImmediately();
-
-            _ScrollPrueferAktivieren = false;
-
-            if (pContact.HasUnreadMessages)
-            {
-                pContact.HasUnreadMessages = false;
-
-                Clientlist.Items.Refresh();
-            }
-
-            var currentContact = pContact;
-            pContact.IsNewMessage = false;
-
-            var shouldChangeIcon = _ContactList.Any(contact => contact.IsNewMessage);
-            if(shouldChangeIcon)
-            {
-                ContainingWindow.Icon = Utils.ConvertIconToImageSource(Resource.ownchat_favicon);
-            }
-
-            CurrentContact = currentContact;
-
-            if(Clientlist.Items.Contains(pContact))
-            {
-                Clientlist.SelectedItem = pContact;
-            }
-
-            _ChatMessages.Clear();
-
-            Chat.LoadChatMessagesForContactAsync(currentContact, GetFirstMessage(), chatMessages =>
-            {
-                this.Dispatch(() =>
+                if (pContact == null)
                 {
-                    _ChatMessages.AddRangeIfElementsNotIn(chatMessages);
+                    return;
+                }
 
-                    WpfUtils.ScrollToBottomOfListBox(ChatListBox);
+                ShouldInterruptContactsThread = true;
 
-                    ChatListBox.ContextMenu = Chat.ErstelleKontextMenue();
-                    SetContextHandler();
-                    _ScrollPrueferAktivieren = true;
+                StartWaitingImmediately();
 
-                    ListenForMessages();
-                    Cursor = Cursors.Arrow;
+                _ScrollPrueferAktivieren = false;
 
-                    WriteToNewSyncFile();
+                if (pContact.HasUnreadMessages)
+                {
+                    pContact.HasUnreadMessages = false;
 
-                    ShouldInterruptContactsThread = false;
+                    Clientlist.Items.Refresh();
+                }
 
-                    EndWaiting();
+                var currentContact = pContact;
+                pContact.IsNewMessage = false;
+
+                var shouldChangeIcon = _ContactList.Any(contact => contact.IsNewMessage);
+                if (shouldChangeIcon)
+                {
+                    ContainingWindow.Icon = Utils.ConvertIconToImageSource(Resource.ownchat_favicon);
+                }
+
+                CurrentContact = currentContact;
+
+                if (Clientlist.Items.Contains(pContact))
+                {
+                    Clientlist.SelectedItem = pContact;
+                }
+
+                _ChatMessages.Clear();
+
+                Chat.LoadChatMessagesForContactAsync(currentContact, GetFirstMessage(), chatMessages =>
+                {
+                    this.Dispatch(() =>
+                    {
+                        _ChatMessages.AddRangeIfElementsNotIn(chatMessages);
+
+                        WpfUtils.ScrollToBottomOfListBox(ChatListBox);
+
+                        ChatListBox.ContextMenu = Chat.ErstelleKontextMenue();
+                        SetContextHandler();
+                        _ScrollPrueferAktivieren = true;
+
+                        ListenForMessages();
+                        Cursor = Cursors.Arrow;
+
+                        WriteToNewSyncFile();
+
+                        ShouldInterruptContactsThread = false;
+
+                        EndWaiting();
+                    });
                 });
-            });
+            }
+            catch(Exception exception)
+            {
+#if DEBUG
+                var desktop = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory);
+
+                using(var fileStream = new FileStream(Path.Combine(desktop, "ownchat_log.txt"), FileMode.OpenOrCreate))
+                {
+                    using(var streamWriter = new StreamWriter(fileStream))
+                    {
+                        streamWriter.WriteLine(exception.ToString());
+                    }
+                }
+#endif
+
+                MessageBox.Show(exception.Message, "Fehler", MessageBoxButton.OK, MessageBoxImage.Error);
+            }
         }
 
         private void SetContextHandler()
diff --git a/ChatController/HauptKlassen/Chat.cs b/ChatController/HauptKlassen/Chat.cs
index 0b8ba4e..f3527ac 100644
--- a/ChatController/HauptKlassen/Chat.cs
+++ b/ChatController/HauptKlassen/Chat.cs
@@ -255,7 +255,7 @@ namespace ChatController.HauptKlassen
                 {
                     var messageCounter = JsonConvert.DeserializeObject<MessageCounter>(response.Content);
 
-                    callback?.Invoke(messageCounter.MessageCount);
+                    callback?.Invoke(messageCounter?.MessageCount ?? 0);
                 });
             }
             catch(Exception exception)
@@ -1028,8 +1028,11 @@ namespace ChatController.HauptKlassen
             try
             {
                 _Contacts.Clear();
-
-                _Contacts.AddRange(GenerateContactsFromServerResponse(chatDaten.Response.Groups.ToArray()));
+                
+                if(chatDaten?.Response != null)
+                {
+                    _Contacts.AddRange(GenerateContactsFromServerResponse(chatDaten.Response.Groups.ToArray()));
+                }
 
                 return _Contacts;
             }
diff --git a/ChatController/LoginControl.xaml.cs b/ChatController/LoginControl.xaml.cs
index 2342200..8d0d4de 100644
--- a/ChatController/LoginControl.xaml.cs
+++ b/ChatController/LoginControl.xaml.cs
@@ -101,11 +101,6 @@ namespace ChatController
             //_ChatCode = "K2UPV-qrirb";
             //_Benutzername = "lyndon";
             //Password = "lyndon2travemünde";
-
-            _Kundennummer = "4368658436";
-            _ChatCode = "B7x0b-FhhJA";
-            _Benutzername = "jettenl";
-            Password = "n8-yR+3Q=6nX#";
 #endif
         }
 
diff --git a/PrototypChat/.vs/PrototypChat/v16/.suo b/PrototypChat/.vs/PrototypChat/v16/.suo
index e198421..ca1b2d1 100644
Binary files a/PrototypChat/.vs/PrototypChat/v16/.suo and b/PrototypChat/.vs/PrototypChat/v16/.suo differ