Grenade Launchers handling means it always clicks empty

### Testmerges

N/A

### Round ID

N/A

### Description of the bug

Doesn't really affect it too much. But because of how it's coded to handle all of the stuff after the attack. When the initial stuff happens in handle_fire() it believe's it's empty.
Then after that it'll do it's afterattack where it actually handles firing.

### What's the difference with what should have happened?

It shouldn't think it's empty. It should probably just be refactored to use gun.dm procs rather than some weird afterattack stuff.

### How do we reproduce this bug?

1. Attempt to fire a loaded grenade launcher
2. It says it clicks in chat, but the sound gets drowned out by the firing sound if it actually does fire.
3. Cry at the jank code
...

### Issue Bingo

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