#1 'Doinkd' segfaults (signal 11) when started as a service.

[Marcin Sielski]

When 'Doinkd' is started as a service and there is no users actualy logged into system it segfaults (signal 11).

There is a bug in the 'chk_maxuser' function. When it receives as a prameter 'user==NULL' following condition:

if (user->mgroup != 0) {

causes segfault. Bug can be very easy reproduced and
tracked by gdb (core dumps have to be enabled).

Tested fix is:

if (user != NULL && user->mgroup != 0) {

[Luke Dennis]

I think this should instead be

if (n_users && user->mgroup != 0) {

as user is uninitialised, and therefore not guaranteed to be NULL