Not really much to say here. Maybe some kind of compatibility error?
https://www.dropbox.com/s/rre8pqsqk6kma90/crash-2015-04-13_17.02.01-server.txt?dl=0

What did you do to have this happen?

I get the same thing. It's on server start-up, not on any particular action.

Fixed in v6.0.2.