git version?
im using nodebb 0.9.3
there are different versions in 0.9.3?
I added some user in the chat with empty user, now it seems to work.
there is no posibilty to delete a whole chat.
Thanks for reporting. This should be fixed in 1.13.2. https://github.com/NodeBB/NodeBB/commit/3cca929a889120c089ce508a74ce40789e0c02d0