fix crash when resizing tiled scratchpad windows

Splitting and then hiding a scratchpad container results in
a segfault.

fixes swaywm#6693

sway/commands/resize.c

@@ -51,11 +51,13 @@ struct sway_container *container_find_resize_parent(struct sway_container *con,
 
 	while (con) {
 		list_t *siblings = container_get_siblings(con);
-		int index = container_sibling_index(con);
-		if (container_parent_layout(con) == parallel_layout &&
+		if (siblings){
+			int index = container_sibling_index(con);
+			if (container_parent_layout(con) == parallel_layout &&
 				siblings->length > 1 && (allow_first || index > 0) &&
 				(allow_last || index < siblings->length - 1)) {
-			return con;
+					return con;
+			}
 		}
 		con = con->pending.parent;
 	}
@@ -302,8 +304,11 @@ static struct cmd_results *resize_set_tiled(struct sway_container *con,
 			}
 			if (parent) {
 				width->amount = parent->pending.width * width->amount / 100;
-			} else {
+			} else if (con->pending.workspace) {
 				width->amount = con->pending.workspace->width * width->amount / 100;
+			} else {
+				return cmd_results_new(CMD_FAILURE,
+						"Cannot resize a tiled container with no parent or workspace");
 			}
 			width->unit = MOVEMENT_UNIT_PX;
 		}
@@ -323,8 +328,11 @@ static struct cmd_results *resize_set_tiled(struct sway_container *con,
 			}
 			if (parent) {
 				height->amount = parent->pending.height * height->amount / 100;
-			} else {
+			} else if (con->pending.workspace) {
 				height->amount = con->pending.workspace->height * height->amount / 100;
+			} else {
+				return cmd_results_new(CMD_FAILURE,
+						"Cannot resize a tiled container with no parent or workspace");
 			}
 			height->unit = MOVEMENT_UNIT_PX;
 		}