I would get a peice of glass and take out the old and put in the new. Or for a cheaper/quicker rig. You could get a peice that would cover the crack and just cover it. Its not leaking now and it is probably double glass on the bottom or 2 peices so just covering it should be fine. Use gobs of silicone.
IDK if that would be a good idea because the crack could spread at anytime the glass is already weakend. But id say go with getting a piece the size of the bottom but just small enough obviously so it fits inside and silicon around all of it that should work and i think itd be the best rout to go.