When a guest account that doesn't exist is specified, smbd starts just fine, resulting in a crash when trying to connect as a guest user.
This is fixed in master by commit 51567de6d7d91f727a2135cd2d5434f85db6d45a
This fix should probably be backported to samba 3.6, as it is an obvious fix.
The problem was detected based on this debian bug report:
Thanks in advance!
Ivo De Decker
This bug is fixed in 3.6.6