Author: Iñaki Arenaza
MDL-16168 auth/cas CAS crashes if no LDAP is set up
Pending fix for Moodle 2.x. Credit goes to Ivan Dackiewicz.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=beb807e033dcd64d0b464f6d30486e963c4b0d11
http://github.com/moodle/moodle/commit/beb807e033dcd64d0b464f6d30486e963c4b0d11
+ 2.0 en [noldapserver,auth_cas]