crash when uploading a folder

Dragging a folder into a directory without permissions will cause an immediate exit, but dragging a file won’t; it will only show a failure message.

Reproduce the crash by dragging a folder into a directory without permissions, then compare it with dragging a file into the same location. Trace the folder-upload handling from that interaction and verify that the completed fix keeps the application running and shows a failure message instead of exiting.

Written by the indexing model from the issue text.