wys-audio: Guard public methods

This makes sure we get the right type passed in and
also don't crash when there's no modem.
5 jobs for master in 5 minutes and 54 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #326964
librem5
build:native

00:00:40

 
  Package
passed #326965
librem5
package:deb-debian-buster

00:01:09

passed #326966
librem5:arm64
package:deb-debian-buster:arm64

00:04:11

 
  Test Package
passed #326967
librem5
autopkgtest-debian-buster-package

00:01:00

passed #326968
librem5
lintian-debian-buster-package

00:00:59