Return map & MaplePacketEncoder & Quest status patch

Fixed null pointer issue when trying to use return scroll on maps such as Mu Lung.
Fixed a critical deadlock issue with MaplePacketEncoder.
Fixed a critical DB leak regarding player's quest status.

src/net/server/channel/handlers/ItemPickupHandler.java

@@ -44,6 +44,7 @@ public final class ItemPickupHandler extends AbstractMaplePacketHandler {
         int oid = slea.readInt();
         MapleCharacter chr = c.getPlayer();
         MapleMapObject ob = chr.getMap().getMapObject(oid);
+        if(ob == null) return;
         
         Point charPos = chr.getPosition();
         Point obPos = ob.getPosition();