How delete a custom propertie ?

[Ludovic Thebault]

> put the customkeys of this stack into ck
> put lineoffset("cp1",ck) into the_line
> if the_line is not 0 then  ## always check...
>    delete line the_line of ck
> end if
> set the customkeys of this stack to ck
> ...
>
> Totally intuitive, isn't it ? ;-) 


Thanks !