Fixed NullPointerException

Caused by: java.lang.NullPointerException: Cannot invoke "java.lang.Boolean.booleanValue()" because the return value of "com.sedmelluq.discord.lavaplayer.tools.JsonBrowser.as(java.lang.Class)" is null

womp womp deezer

main/src/main/java/com/github/topi314/lavasrc/deezer/DeezerAudioSourceManager.java

@@ -302,7 +302,8 @@ private List<AudioTrack> parseTracks(JsonBrowser json, boolean preview) {
 	}
 
 	private AudioTrack parseTrack(JsonBrowser json, boolean preview) {
-		if (!json.get("readable").as(Boolean.class)) {
+		Boolean readable = json.get("readable").as(Boolean.class);
+		if (readable == null || !readable) {
 			throw new FriendlyException("This track is not readable. Available countries: " + json.get("available_countries").text(), FriendlyException.Severity.COMMON, null);
 		}
 		var id = json.get("id").text();