fix: onDrop json parse issue

packages/nc-gui/components/tabs/Smartsheet.vue

@@ -87,7 +87,7 @@ const onDrop = async (event: DragEvent) => {
   event.preventDefault()
   try {
     // Access the dropped data
-    const data = JSON.parse(event.dataTransfer!.getData('text/json'))
+    const data = JSON.parse(event.dataTransfer!.getData('text/json') || '{}')
     // Do something with the received data
 
     // if dragged item is not from the same source, return