Wow, that’s new. Obviously some local resident decided to be clever. I suggest taking a chisel and hammer next time you go and removing the glass (plus maybe a caulking gun and some white filler putty for covering up the remains). Should be a pretty easy repair job. I cannot think of anything useful the Council can do about this, there already is a No Climbing sign. Whoever the prick is, he will soon see that there is more of us than him.