Fixed null pointer deref when we try to autojoin a channel of a network not
in the network list.
Followed richtroye suggestion and implemented the net == NULL guard in
servlist_favchan_find().
Restored inbound.c to make the pull request cleaner.
Merge pull request #622 from orium/null-ptr-favchan-fix

Fixed null pointer deref when we try to autojoin a channel