Fixed NPE during login.

Not sure how a player could NOT have an IP address at this point?  But
logs from customers show it happens somehow.

src/me/ryanhamshire/GriefPrevention/PlayerEventHandler.java

@@ -689,6 +689,8 @@ class PlayerEventHandler implements Listener
 		
 		//ensure we're not over the limit for this IP address
         InetAddress ipAddress = playerData.ipAddress;
+        if(ipAddress != null)
+        {
             String ipAddressString = ipAddress.toString();
             int ipLimit = GriefPrevention.instance.config_ipLimit;
             if(ipLimit > 0 && !player.hasAchievement(Achievement.MINE_WOOD))
@@ -711,6 +713,7 @@ class PlayerEventHandler implements Listener
                 }
             }
         }
+	}
 	
 	//when a player spawns, conditionally apply temporary pvp protection 
     @EventHandler(ignoreCancelled = true, priority = EventPriority.MONITOR)