trivial fix, don't unregister reader if detached
trivial fix, don't unregister reader if detached

Change-Id: Id19f846a9e0c812bbe073b759e9aba18f7ff5063

realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core