What usually happens is there are tabs on one of the inner door panels that holds the glass up.
If one tabs breaks, the other one soon will, then the glass slips down.
If the mesh / screen is still in place and undamaged, and the door is otherwise undamaged, there shouldn't be any leakage.
You or someone you know may be able to take the door apart and use epoxy to fashion new retainers for the glass.
Or you can usually order the specific door panel piece that you need but if you want to, please reply back with your brand and model number so we can help you.You have to separate the door panels (as shown in the attached photo)
and then you'll see the previously hidden screws you need to remove.
Or you can watch a YouTube video (not a video I
made) that demonstrates how it's done.
You can usually find
helpful exploded view diagrams and order parts by entering your full
model number here.
happy to help you with free advice and we'd appreciate your thoughtful
rating of our answer.