Add array bounds check in compareSubmit before accessing drag data

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/views/Files/FilesPage.vue

@@ -841,6 +841,7 @@ function secondaryDragDelete() {
  * Enter the Compare page
  */
 function compareSubmit() {
+  if (primaryDragData.value.length === 0 || secondaryDragData.value.length === 0) return;
   const primaryType = primaryDragData.value[0].type;
   const secondaryType = secondaryDragData.value[0].type;
   const primaryId = primaryDragData.value[0].id;