List View: Fix stuck dragging mode in UI in Firefox when dealing with…

… deeply nested lists (#60845)



Co-authored-by: andrewserong <andrewserong@git.wordpress.org>
Co-authored-by: ramonjd <ramonopoly@git.wordpress.org>
Co-authored-by: diggeddy <diggeddy@git.wordpress.org>

packages/block-editor/src/components/list-view/use-list-view-drop-zone.js

@@ -556,9 +556,14 @@ export default function useListViewDropZone( {
 	const ref = useDropZone( {
 		dropZoneElement,
 		onDrop( event ) {
+			throttled.cancel();
 			if ( target ) {
 				onBlockDrop( event );
 			}
+			// Use `undefined` value to indicate that the drag has concluded.
+			// This allows styling rules that are active only when a user is
+			// dragging to be removed.
+			setTarget( undefined );
 		},
 		onDragLeave() {
 			throttled.cancel();