gaussRIFLE sound keeps playing after switching weapon

[Lonami]

Steps to reproduce

1. Select gaussRIFLE.
2. Hold fire.
3. Switch to another weapon (i.e. the first one).

Current behaviour

gaussRIFLE's sound keeps playing, when it should not. This may be similar to #343

[Rei]

let weapons handle being switched; gaussRIFLE stops charging sound, resolves #382

→ <<cset c0bebc706323>>