Fix exception when getting displayname

Fix exception if null values are in settings groups.yml

Essentials/src/com/earth2me/essentials/settings/Chat.java

@@ -17,7 +17,7 @@ public class Chat implements StorageObject
 		"Disable this if you have any other plugin, that modifies the displayname of a user.",
 		"If it is not set, it will be enabled if EssentialsChat is installed, otherwise not."
 	})
-	private Boolean changeDisplayname;
+	private Boolean changeDisplayname = true;
 	private String displaynameFormat = "{PREFIX}{NICKNAMEPREFIX}{NAME}{SUFFIX}";
 	@Comment(
 	{

Essentials/src/com/earth2me/essentials/settings/GroupsHolder.java

@@ -59,7 +59,10 @@ public class GroupsHolder extends AsyncStorageObjectHolder<Groups> implements IG
 			{
 				if (player.isAuthorized("essentials.groups." + entry.getKey()))
 				{
+					if(entry.getValue() != null)
+					{
 					list.add(entry.getValue());
+					}
 				}
 			}
 			return list;