Fix NPE

Signed-off-by: Lixfel <agga-games@gmx.de>

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

@@ -46,7 +46,7 @@ public class ArenaCommand extends BasicCommand {
         }
 
         Subserver subserver = Subserver.getSubserver(server);
-        if(subserver.getType() != Servertype.ARENA) {
+        if(subserver == null || subserver.getType() != Servertype.ARENA) {
             Message.send("ARENA_NOT_FOUND", player);
             return;
         }