CMP vendor sidearm selection

[Googles-Hands]

Testmerges:

#1224
#1556
#1350
#1274
#1475

Difference between expected and actual behavior

When selecting the M4A3 sidearm, you only get vended an empty pistol rig instead of a filled one. Might happen to the other sidearm selections as well. Probably happened due to #1457 (which is still a bad PR, bring back custom M4A3 for officers reeeeeee).

Steps to reproduce

Play as CMP, select the "M4A3" sidearm and get vended an empty pistol holster rig.

Issue bingo (not required to be all checked)

• 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)