Spawn in a non-existent chunk.

[tigerw]

Mobs correctly aren't spawning, however, the provided message indicates that a cPickup (not a mob) is being created. The console command 'destroyentities' will destroy all current entities. To prevent all entities from spawning however, you'll probably have to edit the code and add a 'return false' in cWorld::SpawnEntity (or something like that).