Better error handler

[btzr-io]

audioElement.onerror = function() {
    let s = "";
    let err = audioElement.error;
    
    switch(err.code) {
      case MediaError.MEDIA_ERR_ABORTED:
        s += "The user canceled the audio.";
        break;
      case MediaError.MEDIA_ERR_NETWORK:
        s+= "A network error occurred while fetching the audio.";
        break;
      case MediaError.MEDIA_ERR_DECODE:
        s+= "An error occurred while decoding the audio.";
        break;
      case MediaError.MEDIA_ERR_SRC_NOT_SUPPORTED:
        s+= "The audio is missing or is in a format not supported by your browser.";
        break;
      default:
        s += "An unknown error occurred.";
        break;
    }
    
    let message = err.message;
    
    if (message && message.length) {
      s += " " + message;
    }
    
    displayErrorMessage("<strong>Error " + err.code + ":</strong> " + s + "<br>");
  };

https://developer.mozilla.org/en-US/docs/Web/API/MediaError/message