Fix compiler warnings, and a bug where the `snd_handle` of
`SoundBankInfo` was never set, leading to sound banks never unloading.
The game relies on unloading soundbanks to make sure certain sounds
don't play, like the blue gun 1 fire noise when using blue gun 2.
---------
Co-authored-by: water111 <awaterford1111445@gmail.com>