Currently, after swapping contents there are aliases for non-existent translations which prevent proper redirection from happening after moving content to another location.

Steps to reproduce:
1. Add a new language to eZ Publish e.g. French.
2. Create content A which has two translations e.g. English and French.
3. Create content B which has only an English translation.
4. Swap content A with content B.
5. Move content B to another location.
6. Try to access content B using its old URL alias.

Result:
There is no redirect to the new URL. Also, there are two URL aliases, for content B even though there was only one translation for it.