When moving dir to destination that already exists, the source is simply deleted

[captbaritone]

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Steps to reproduce:

Move a directory to a location that already exists with clobber set to false.

Expected behavior

An error is passed to the callback.

Actual behavior

The source directory is deleted and no copy is made

Reason

npc does not seem to error when asked to copy a directory on top of an existing file/directory, it just fails silently.