fix: Password success banner if not succeeded

lib/views/settings.dart

@@ -82,16 +82,18 @@ class _SettingsState extends State<Settings> {
       ],
     );
     if (input == null) return;
-    await showFutureLoadingDialog(
+    final success = await showFutureLoadingDialog(
       context: context,
       future: () => Matrix.of(context)
           .client
           .changePassword(input.last, oldPassword: input.first),
     );
+    if (success.error == null) {
       await FlushbarHelper.createSuccess(
               message: L10n.of(context).passwordHasBeenChanged)
           .show(context);
     }
+  }
 
   void _deleteAccountAction(BuildContext context) async {
     if (await showOkCancelAlertDialog(