I'm not sure I'd risk breaking the glass to have a hardware store fix it and they'd just crimp it again anyway. If possible, that it doesn't interfere with mounting, Bolt-On or even Bolt-In a Flat Corner Brace (
You just drill the frame (outside of the glass' seat) and Bolt (or Long Rivet) braces on both sides (inside and outside of both corners). If you're really lucky the corners are hollow and you can put 1 or 2 braces inside to then Bolt or Rivet. This is much more solid than the original crimps.