Fix scoreboard cleanup

BauSystem/BauSystem_Main/src/de/steamwar/bausystem/features/world/BauScoreboard.java

@@ -131,6 +131,7 @@ public class BauScoreboard implements Listener {
 
     @EventHandler
     public void onPlayerQuit(PlayerQuitEvent event) {
+        SWScoreboard.impl.removeScoreboard(event.getPlayer());
         ADDITIONAL_SCOREBOARD_LINES.remove(event.getPlayer());
     }
 }

SpigotCore/SpigotCore_Main/src/de/steamwar/scoreboard/SWScoreboard.java

@@ -67,7 +67,9 @@ public class SWScoreboard {
     }
 
     public void removeScoreboard(Player player) {
-        player.getScoreboard().getObjective(SIDEBAR).unregister();
+        if (player.getScoreboard().getObjective(SIDEBAR) != null) {
+            player.getScoreboard().getObjective(SIDEBAR).unregister();
+        }
         playerBoards.remove(player);
     }
 }