The change is because the requested contact does not exist.
For instance, if the user invites a nonexistent contact to a chatroom or attempts to call a nonexistent contact, this could be indicated by the CM adding that contact's handle to remote-pending for reason None or Invited, then removing it for reason Invalid_Contact. In the case of a 1-1 StreamedMedia call, the CM SHOULD remove the self handle from the Group in the same signal. For 1-1 calls, the call terminates as a result of removing the remote contact, so the SelfHandle should be removed at the same time as the remote contact and for the same reason. If a contact is removed from a group for this reason, the equivalent D-Bus error is org.freedesktop.Telepathy.Error.DoesNotExist.