Volume can't be zero (0.0) in the sounds.json

If a volume of a sound is set 0.0, the whole sounds.json will be regarded invalid, including other valid entries.

{
  "sound1": {
    "subtitle": "sound1",
    "sounds": [
      {
        "name": "note/bell",
        "pitch": 0.890899
      }
    ]
  },
  "sound2": {
    "subtitle": "subtitles.traindoor.warning",
    "sounds": [
      {
        "name": "note/bell",
        "volume": 0.0
      }
    ]
  }
}

if the sound2 volume is 0.0, then the sound1 and sound2 are both ignored.

See also MC-201966