Fix bug with focus parent

Thanks anon

sway/commands.c

@@ -113,10 +113,12 @@ int cmd_focus(struct sway_config *config, int argc, char **argv) {
 		move_focus(MOVE_DOWN);
 	} else if (strcasecmp(argv[0], "parent") == 0) {
 		swayc_t *current = get_focused_container(&root_container);
+		if (current && current->parent) {
 			current->parent->focused = NULL;
 			unfocus_all(current->parent);
 			focus_view(current->parent);
 		}
+	}
 	return 0;
 }