The function `gnus-registry-handle-action' is meant to handle message
entries when messages are being moved/copied/deleted. Code comments
indicate that if a message is being "moved to nowhere" it's actually
being deleted, but the code doesn't actually delete the entry. In fact,
because it unilaterally creates an entry before checking what to do with
it, but then never deletes it, it will *create* entries for messages
being deleted, or moved into groups that should be ignored.

The attached patch confirms that registry information about the message
should actually be kept, before keeping it.

Eric