anchor.diff:  
   handle_call(get_config, _, #state{holder=Holder, timer=Timer}=State) ->
       Conf = observer_lib:timer_config(Timer),
  -    Accum = call(Holder, {get_accum, self()}),
  +    Accum = case safe_call(Holder, {get_accum, self()}) of
  +                Bool when is_boolean(Bool) -> Bool;
  +                _ -> false
  +            end,
       {reply, Conf#{acc=>Accum}, State};
   
   handle_call(Msg, _From, State) ->
  
positive.code: 		wxMenu:append(Menu, ?ID_TRACE_NAMES,
  			      "Trace selected processes by name (all nodes)",
  			      [{help, ?TRACE_NAMES_STR}]),
  		wxMenu:append(Menu, ?ID_KILL, "Kill process " ++ pid_to_list(P)),
  		wxWindow:popupMenu(Panel, Menu),
  		wxMenu:destroy(Menu),
  
negative.code: -define(ID_TRACE_NEW, 208).
  -define(ID_TRACE_ALL, 209).
  -define(ID_ACCUMULATE, 210).
  -define(ID_GARBAGE_COLLECT, 211).
  
  -define(TRACE_PIDS_STR, "Trace selected process identifiers").
  -define(TRACE_NAMES_STR, "Trace selected processes, "
  