There's no such identifier as $theme

You can do it as such:

on *:TEXT:!cf *:#:{
  if ($nick($chan,$nick,@&~)) && ($istok(on off,$2,32)) {
    set $+(%,con.,$chan) $iif($pos($2,on,1),0,1)
    msg $chan toclafane's coin flip is now switched $2
  }
}

Saves you about 78 bytes and the repetition.