You may want to check $nick != $me so that you would be able to override your own script if need be.

Code:
on @*:MODE:#: {
  if (G isincs $chan(#).mode && $nick != $me) mode # -G
}


Also if a server changes the mode to +G (possible scenario) you may need the same script running from an ON SERVERMODE event (I'm not sure if servers trigger ON MODE in addition to ON SERVERMODE).

- argv[0] on EFnet #mIRC
- "Life is a pointer to an integer without a cast"