bookmark-list: clear state when loading operation fails

When the load operation for the bookmark file fails (e.g. because we
have no file at all), don't forget to clear the queue state.

src/nautilus-bookmark-list.c

@@ -446,6 +446,7 @@ load_callback (GObject *source,
 	contents = g_simple_async_result_get_op_res_gpointer (G_SIMPLE_ASYNC_RESULT (res));
 
 	if (contents == NULL) {
+		op_processed_cb (self);
 		return;
 	}