group_roles_module - Avoid e-notice by early return

If there is no contact id then there is nothing further to do. However, the line which allocates a contact id gives an e-notice in this instance.  Add early return if no contact_id
CRM-14171 Adding a warning for risky permissions given to anoymous users.
Merge pull request #134 from eileenmcnaughton/patch-4

group_roles_module - Avoid e-notice by early return
Merge remote-tracking branch 'upstream/7.x-4.4' into 7.x-4.4-7.x-master-2014-04-30-12-58-05
Merge pull request #137 from generalredneck/CRM-14171

CRM-14171 Adding a warning for risky permissions given to anoymous users.