Hotfix npe

src/de/steamwar/bungeecore/commands/TypeMappers.java

@@ -88,6 +88,7 @@ public class TypeMappers {
             public Collection<String> tabCompletes(CommandSender sender, String[] previousArguments, String s) {
                 if (previousArguments.length == 0) return null;
                 ArenaMode arenaMode = ArenaMode.getByChat(previousArguments[previousArguments.length - 1]);
+                if (arenaMode == null) return null;
                 List<String> stringList = new ArrayList<>(arenaMode.getMaps());
                 stringList.add("random");
                 return stringList;