Right, not structural. I have a few used aquariums that have broken trim. No problem.
Especially in that area. It is supported on either side of the gape so should be fine. A patch would have to be perfectly matched to do any good. Something soft like silicone isn't going to support anything.(although I have done it anyway) and something hard must be exactly the same size and compression strength as the trim. If you wedge something in that's too short (or too soft) it won't do anything. If it is too tall (or too hard) it will lift the glass in that area more than others and cause stress and cracking.
Leave it alone. Show the ugly side to the wall.