Prevent potential null pointer dereference
Prevent potential null pointer dereference

This commit adds checks to ensure cfg->name_attributes is not null before
it is used in mag_get_name_attributes.

(Reworded commit message)

Reviewed-by: Simo Sorce <simo@redhat.com>

Close #64

devurandom/mod_auth_gssapi,frenche/mod_auth_gssapi,frenche/mod_auth_gssapi,devurandom/mod_auth_gssapi,devurandom/mod_auth_gssapi,frenche/mod_auth_gssapi,uhd-urz/mod_auth_gssapi,frenche/mod_auth_gssapi,uhd-urz/mod_auth_gssapi,uhd-urz/mod_auth_gssapi