[NTG-context] Testing non-existent counter in Lua

Hi, all. How do I know (due Lua) that the counter has not been defined in ConTeXt (through the command newcount)? I am trying testing : if tex.count.mycount == nil then... or if tex.count.mycount == 'error' then... then when counter isnt defined due \newcount\mycount, then test ending with error message. When counter is defined due \newcount\mycount, \mycount=1 then test if tex.count.mycount == 1 then... is OK... Thanx, Jaroslav