Head to MTA folder > mods > dearthmatch > resources > CITvehMods and remove it from there, then login, and quit MTA once again. Add it again to where it was in case it wasn't added by itself (Not sure if it gonna be added by itself or nah) add it anyways.This way should make the GUI not empty anymore.
For the default CIT mod thing, you can try /connect mtasa://94.23.158.180:22003 and give it some time to download them after you log in.For the vehmods and gunmods GUIs being empty, it should've been fixed when you deleted the resources so idk tbh.