Merge pull request #1804 from martinetd/crashes

Fix crashes

sway/input/seat.c

@@ -491,6 +491,9 @@ void seat_set_focus_warp(struct sway_seat *seat,
 			ipc_event_workspace(last_ws, container, "focus");
 			if (!workspace_is_visible(last_ws)
 					&& last_ws->children->length == 0) {
+				if (last_ws == last_focus) {
+					last_focus = NULL;
+				}
 				container_destroy(last_ws);
 			}
 		}

sway/tree/container.c

@@ -104,7 +104,7 @@ static void _container_destroy(struct sway_container *cont) {
 	if (cont->children != NULL && cont->children->length) {
 		// remove children until there are no more, container_destroy calls
 		// container_remove_child, which removes child from this container
-		while (cont->children != NULL) {
+		while (cont->children != NULL && cont->children->length > 0) {
 			struct sway_container *child = cont->children->items[0];
 			container_remove_child(child);
 			_container_destroy(child);