Fixed critical bug EXT-4947 (Viewer crashes after 'See my online status'...

Fixed critical bug EXT-4947 (Viewer crashes after 'See my online status' check-box was checked for deleted from friends avatar)
 - added updating of allowed rights when friendship is terminated/started to disable/enable checkboxes
 - also added validation of avatar's relationship before committing and log a warning if it is absent.

--HG--
branch : product-engine