Fixed NPE on missing kick-reason - http://redmine.bukkit.org/issues/359

src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java

@@ -103,7 +103,7 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
     }
 
     public void kickPlayer(String message) {
-        entity.a.a(message);
+        entity.a.a(message == null ? "" : message);
     }
 
     public void setCompassTarget(Location loc) {