I have such crashes too. if you are connected through some remote admin program you will actually see more of what happened than the console log. it seems the server just stopped logging some time before the server shuts down/crashes.
what you see in console is just like a normal shutdown..
Shutting down server..
Shutting down admin connection..
and maybe 1 or 2 more lines.
its pretty rare though, maybe once a week or something, so i dont mind it too much. i cant say wether or not its related to the server being full on my end though, i havent noticed or specifically looked at it.