Accidentally removed part of rubber strip between bathtub and glass while replacing silicone caulk
It is moldy and your best bet would be to remove the glass and re-install it as if it were new. Remove all the caulk, rubber seal and clean the bottom and sides of the glass frame. Scrape all surfaces with a single edge blade to remove any film and then clean with vinegar to kill off any remaining mold. Let the surfaces totally dry. Put a bead of quality silicone caulk on the tub and wall surfaces where the glass frame will sit. Mount the glass/doors and then caulk the entire inside of the tub, tub to glass, tub to wall and wall to glass Also caulk the miter joints on the frame. Wait a day and then caulk the entire outside of the tub. 

If you can't remove the glass, do everything else and try to clean under the frame as good as possible. Scrape, clean, dry and caulk like above. Good luck.