It all depends on the thickness of the glass and whether you want to take such a chance when the fix is so simple. It doesn't take a rocket scientist to put in a glass cross brace. You do not even need to remove a broken brace IE plastic brace to put in a glass brace. Just place it directly below the broken brace. The same hassles is there as in a installation without the brace and that is you have to hold it in place until the caulking is cured. Be,Believe it or not glass is officially still a liquid and is still flowing under rules of gravity. Very, very slowly but still flowing. Old window panes are always measurably thicker at the bottom of the pane. Glass bends. Just a little, then it breaks catastrophically, and lots of money time and dreams are wasted.