sand off the glass about 1 inch around the crack, feathering the glass edge out another inch. Lay a new piece of glass over the sanded area. When the epoxy has cured, sand down the edges and apply a fill coat larger than the patch area. When the epoxy cures, sand again.

It should take less than an hour of effort, not including epoxy cure times. There will be no compromise of strength and should be invisible when complete.