NEXUS-6282: Added nullcheck.
Merge pull request #374 from sonatype/NEXUS-6282-nullcheck

NEXUS-6282: Added nullcheck.
Merge remote-tracking branch 'origin/master' into realm-caches

Conflicts:
	components/nexus-ldap-common/src/main/java/org/sonatype/security/ldap/realms/AbstractLdapAuthenticatingRealm.java