Tolerate an empty client_servergroups in Client.getServerGroups

Some servers list a client with an empty client_servergroups; parsing it
threw NumberFormatException and aborted iterating the whole client list.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main/java/com/github/manevolent/ts3j/api/Client.java

@@ -28,6 +28,7 @@ package com.github.manevolent.ts3j.api;
 
 import java.io.UnsupportedEncodingException;
 import java.net.URLEncoder;
+import java.util.Arrays;
 import java.util.Date;
 import java.util.Map;
 
@@ -130,12 +131,12 @@ public class Client extends Wrapper {
 
 	public int[] getServerGroups() {
 		final String str = get(ClientProperty.CLIENT_SERVERGROUPS);
-		final String[] arr = str.split(",");
-		final int[] groups = new int[arr.length];
-		for (int i = 0; i < groups.length; i++) {
-			groups[i] = Integer.parseInt(arr[i]);
-		}
-		return groups;
+		if (str == null) return new int[0];
+		return Arrays.stream(str.split(","))
+				.map(String::trim)
+				.filter(s -> !s.isEmpty())
+				.mapToInt(Integer::parseInt)
+				.toArray();
 	}
 
 	public int getTalkPower() {