file-transfer: return a value from task

- This fixes "GTask finalized without ever returning (using g_task_return_*()).
This potentially indicates a bug in the program." errors.

document-portal/file-transfer.c

@@ -566,14 +566,17 @@ stop_file_transfers_in_thread_func (GTask        *task,
         }
     }
   G_UNLOCK (transfers);
+  g_task_return_boolean (task, TRUE);
 }
 
 void
 stop_file_transfers_for_sender (const char *sender)
 {
   GTask *task;
+  g_autofree char *name = g_strdup_printf("stop_file_transfers_for_sender(%s)", sender);
 
   task = g_task_new (NULL, NULL, NULL, NULL);
+  g_task_set_name (task, name);
   g_task_set_task_data (task, g_strdup (sender), g_free);
   g_task_run_in_thread (task, stop_file_transfers_in_thread_func);
   g_object_unref (task);