Empty party null leader check.

L2J_Mobius_Classic_Interlude/java/org/l2jmobius/gameserver/model/AbstractPlayerGroup.java

@@ -68,6 +68,11 @@ public abstract class AbstractPlayerGroup
 	 */
 	public int getLeaderObjectId()
 	{
+		final PlayerInstance leader = getLeader();
+		if (leader == null)
+		{
+			return 0;
+		}
 		return getLeader().getObjectId();
 	}
 	

L2J_Mobius_Classic_Interlude/java/org/l2jmobius/gameserver/model/Party.java

@@ -1087,6 +1087,10 @@ public class Party extends AbstractPlayerGroup
 	@Override
 	public PlayerInstance getLeader()
 	{
+		if (_members.isEmpty())
+		{
+			return null;
+		}
 		return _members.get(0);
 	}