UPP Vehicle Ammo reloads at -1, and when unloaded it has negative current rounds (and some assets have no empty rounds icon)

[Yorkoh]

Testmerges

n/a

Round ID

local

Description of the bug

Loading UPP ammo into plain/decrepit but fixed UPP vehicle leads to negative magazines, and then unloading these negative magazines has an item with missing icons

What's the difference with what should have happened?

1. Loading new mags shouldn't create negative rounds in the new magazine.
2. UPP vehicle magazines need icons when they are empty - unless this is just because they are negative?

How do we reproduce this bug?

1. Spawn plain/decrepit UPP vehicle (e.g APC)
2. Spawn appropriate assets & fix the bugger up (including turret)
3. Spawn appropriate ammo for the UPP vehicle
4. Load them into the ammo loader
5. Notice that the new magazine loads in at -1/X e.g. "You begin loading Gshk Minigun Magazine into the Gshk-5000.K minigun. You load Gshk Minigun Magazine into the Gshk-5000.K minigun. Ammo: -1/500 | Mags: 1/2"
6. Interact with the ammo loader, remove this hardpoint's magazine
7. Notice that most UPP magazine assets have no icon for when their magazine is empty
8. Notice that "Something went horribly wrong. Ahelp the following: ERROR CODE R1: negative current_rounds on examine." is in the description when examining them

Issue Bingo

• Issue could be reproduced at least once
• Issue happened in a recent (less than 7 days ago) round
• Couldn't find an existing issue about this (https://github.com/cmss13-devs/cmss13/issues)