You can buy a silicone adhesive to repair the door if it has become unstuck.
The glass will either be glued directly to the door, or there will be some small brackets that are glued to the glass, that locate in the door and hold it in place.
Ensure that the glue you use is intended for the job, otherwise it may not be heat proof for the high temperatures, or food safe.
A company http://ovendoorglue.co.uk offer a small kit for this sort of repair.
Eddie, April 2009