Fixes for logging out the active connection

- Don't crash
- Fall back to WelcomePage

src/app/qml/Main.qml

@@ -267,6 +267,17 @@ Kirigami.ApplicationWindow {
         }
     }
 
+    Connections {
+        target: root.connection
+        function onLoggedOut(): void {
+            root.pageStack.clear();
+            let page = root.pageStack.push(Qt.createComponent('org.kde.neochat.login', 'WelcomePage'), {
+                showExisting: true,
+            }) as WelcomePage;
+            page.connectionChosen.connect(() => root.load())
+        }
+    }
+
     Connections {
         target: AccountRegistry
         function onRowsRemoved() {