Fix null position async errors

src/main/java/wtf/beatrice/limbomanager/objects/LocationCheckRunnable.java

@@ -39,6 +39,9 @@ public class LocationCheckRunnable implements Runnable
             if(player != null) playersToCheck.remove(player);
         }
 
+        if(!Cache.playerIslands.containsKey(player.getName()))
+            return; //it means the player just joined and still didn't get an island (reminder that this is async)
+
         Location playerLocation = player.getLocation();
 
         Coordinates playerIslandCoordinates = Cache.playerIslands.get(player.getName());