Fix memory leak in engineImageLinkDFF

[FileEX]

Fixed #4288

After updating the archive information and then calling the streaming CStreamingSA::ReInit (engineRestreamWorld), the RwObject associated with the original archive was “lost”, and a new one was loaded for the new archive.

Sequence:

link dff -> restream -> keep old RwObject -> create RwObject for new archive

Restart resource:
restore dff (unlink) -> restream -> keep previously loaded new RwObjects -> create RwObject from original archive

With every subsequent call to engineImageLinkDFF, new RwObjects were created without removing the previous ones. As a result, after each resource restart or reconnect, the number of RwObjects kept increasing, depending on how many models were inside the IMG. This is what caused the memory leak.

[Dutchman101]

Good job, but fingers crossed it won't break anything that wasn't immediately obvious in your local tests.