No way to repair it at all we usually end up having the unit replaced..........Only thing you can maybe do is try epoxy or something of that nature but you'll have the glue smell in the unit....

Are you sure this is a crack and not the way the cover is supposed to be?
Looks just too symmetrical and nice to be a crack.

I cannot tell if it is held in by screws. If it is you can remove it and repair it from the back. Use some real duct tape. The stuff they use to seal heating ducts. It is self stick tin foil with a peel off back. You could cut a piece just a little bigger than the crack. Place this over the crack from the back tin foil facing out. Then use another piece over this on the back with the sticky side glued to the cover to hold this in place. This way you do not have the sticky side showing into the compartment.

If you cannot get the cover off just use the tape in the compartment.
Use a couple layers for additional strength if you want.

It is a good idea to wipe the area off with isopropyl alcohol before applying the tape. This should clean off any release agent/oil from the surface.

There are a couple types of duct tape try to get the one with a thin layer of glue on the back. The other type has a thicker layer about an eighth of an inch but is not as good.

Getting the compartment apart is a real pain so I would not attempt it.
The best stuff I have found to get rid of odors is ground coffee.