Avoid duplicate counts of the same file being deleted.

src/Form/ConfirmDeleteMediaAndFile.php

@@ -137,9 +137,12 @@ class ConfirmDeleteMediaAndFile extends DeleteMultipleForm {
               $inaccessible_entities[] = $file;
               continue;
             }
+            if (!array_key_exists($file->id(), $delete_files)) {
               $delete_files[$file->id()] = $file;
               $total_count++;
             }
+
+          }
         }
       }