chore: Improve join abandoned invite exception

lib/utils/localized_exception_extension.dart

@@ -44,6 +44,9 @@ extension LocalizedExceptionExtension on Object {
         case MatrixError.M_LIMIT_EXCEEDED:
           return L10n.of(context).tooManyRequestsWarning;
         default:
+          if (exceptionContext == ExceptionContext.joinRoom) {
+            return L10n.of(context).unableToJoinChat;
+          }
           return (this as MatrixException).errorMessage;
       }
     }