allow root as parent

src/Umbraco.Web.UI.Client/src/packages/documents/documents/entity-actions/sort-children-of/repository/sort-children-of.repository.ts

@@ -22,7 +22,7 @@ export class UmbSortChildrenOfDocumentRepository extends UmbControllerBase imple
 	}
 
 	async sortChildrenOf(args: UmbSortChildrenOfArgs) {
-		if (!args.unique) throw new Error('Unique is missing');
+		if (args.unique === undefined) throw new Error('Unique is missing');
 		if (!args.sorting) throw new Error('Sorting details are missing');
 
 		const { error } = await this.#dataSource.sortChildrenOf(args);

src/Umbraco.Web.UI.Client/src/packages/documents/documents/entity-actions/sort-children-of/repository/sort-children-of.server.data.ts

@@ -27,7 +27,7 @@ export class UmbSortChildrenOfDocumentServerDataSource {
 	 * @memberof UmbSortChildrenOfDocumentServerDataSource
 	 */
 	async sortChildrenOf(args: UmbSortChildrenOfArgs) {
-		if (!args.unique) throw new Error('unique is missing');
+		if (args.unique === undefined) throw new Error('unique is missing');
 
 		const sortingMapping = args.sorting.map((item) => ({ id: item.unique, sortOrder: item.sortOrder }));
 

src/Umbraco.Web.UI.Client/src/packages/documents/documents/entity-actions/sort-children-of/repository/types.ts

@@ -1,4 +1,4 @@
 export interface UmbSortChildrenOfArgs {
-	unique: string;
+	unique: string | null;
 	sorting: Array<{ unique: string; sortOrder: number }>;
 }