EntityMetadataWrapperException when OG UI uses invalid group IDs

Problem: if somebody visits http://example.com/node/123invalid then the menu item for $entity_type/%/group is triggered, which has og_ui_get_group_admin() as access callback. That function receives the user supplied identifier from the menu system (in the example this would be "123invalid") and passes it on to further API functions without validation. This then results in an EntityMetadataWrapperException down the line.

EntityMetadataWrapperException: Invalid data value given. Be sure it matches the required data type and format. in EntityDrupalWrapper->set() (line 736 of entity/includes/entity.wrapper.inc).

Solution: either og_ui_get_group_admin() validates the identifier or we use an explicit access callback function that wraps og_ui_get_group_admin() and returns proper TRUE/FALSE values.