anchor.diff:  %
   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   on({l_on_cseq, merge, L1 = #lease{epoch=OldEpoch}, L2, ReplyTo}, State) ->
  -    New = L1#lease{epoch    = OldEpoch + 1,
  -                   version = 0,
  -                   aux     = {invalid, merge, get_range(L1), get_range(L2)},
  -                   timeout = new_timeout()},
  -    ContentCheck = generic_content_check(L1, New, merge_step1),
  -    Self = comm:reply_as(self(), 5, {l_on_cseq, merge_reply_step1,
  -                                     L2, ReplyTo, '_'}),
  -    update_lease(Self, ContentCheck, L1, New, State),
  -    State;
  +    case L2 of
  +        empty ->
  +            log:log("trying to merge with empty lease ?!?"),
  +            State;
  +        _ ->
  +            New = L1#lease{epoch    = OldEpoch + 1,
  +                           version = 0,
  +                           aux     = {invalid, merge, get_range(L1), get_range(L2)},
  +                           timeout = new_timeout()},
  +            ContentCheck = generic_content_check(L1, New, merge_step1),
  +            Self = comm:reply_as(self(), 5, {l_on_cseq, merge_reply_step1,
  +                                             L2, ReplyTo, '_'}),
  +            update_lease(Self, ContentCheck, L1, New, State),
  +            State
  +    end;
   
   on({l_on_cseq, merge_reply_step1, L2, ReplyTo,
       {qwrite_deny, _ReqId, Round, L1, {content_check_failed, 
  
positive.code: 
  on({l_on_cseq, renew_reply,
      {qwrite_deny, _ReqId, Round, Value, {content_check_failed, {Reason, _Current, _Next}}}, 
      New, Mode}, State) ->
      % @todo retry
      log:pal("renew denied: ~p~nVal: ~p~nNew: ~p~n~p~n", [Reason, Value, New, Mode]),
      log:pal("id: ~p~n", [dht_node_state:get(State, node_id)]),
  
negative.code:                 % special case for renew after crash-recovery
                  #lease{epoch = E0, owner = O0, version = V0} 
                    when E0 =:= OldEpoch andalso V0 =:= OldVersion andalso O0 =:= OldOwner
                         andalso NewOwner =/= OldOwner andalso Writer =:= renew_recover ->
                         % after a crash the logical owner should not
                         % have changed. however its pid will have
                         % changed. this special case checks that epoch
  