It's entirely possible, especially on a large span with a thin sheet (like a shower door) to break a piece of glass without shoving it in to something sharp. You can get enough bending moment on a large sheet, especially if the support twists when loaded, to shatter it. That said, at that point a sheet of equivalent but non tempered glass would have already broken.
I like your comment about padding the corners/edges with something like silicon/steel. Probably not needed, but if it adds peace of mind, easy to do. Changes the look a bit, but also possible to reverse if needed.