As the title states, the menu does not open properly, and instead shows an empty GUI
Opening the Ammo storage section still works by shift right clicking

So this is actually caused by no ammo loaded in the vehicle. I have changed the GUI to only show ammo that's loaded instead of a super long list of all ammo that can be shot where it was difficult to see the one you have actually loaded.
It's pretty clear this needs improvement, perhaps just a message "No ammo loaded in the vehicle to select from" displayed similar to how the message is displayed when you can't sleep in bed because it's too early.
Any ideas?

Ya, I think even just a little message when you open the menu, saying no ammo to select, would be prefect