fix a bug where placement indicator doesn't show

apps/designer/app/shared/nano-states/use-subscribe-drag-drop-state.ts

@@ -12,7 +12,9 @@ export const useSubscribeDragAndDropState = () => {
   useSubscribe<"dragStart", DragStartPayload>(
     "dragStart",
     ({ origin, dragItem }) => {
-      setState({ isDragging: true, origin, dragItem });
+      // It's possible that dropTargetChange comes before dragStart.
+      // Sot it's important to spread the current ...state here.
+      setState({ ...state, isDragging: true, origin, dragItem });
     }
   );