Fixes attack cursor not showing up in duels (#5259)

* Fixes #5256.
* Fixes the attack cursor not being displayed when players are in a duel.
Thanks to @roSBK!

src/map/clif.cpp

@@ -6535,7 +6535,7 @@ void clif_map_property(struct block_list *bl, enum map_property property, enum s
 #if PACKETVER >= 20121010
 	struct map_data *mapdata = map_getmapdata(bl->m);
 
-	WBUFL(buf,4) = ((mapdata->flag[MF_PVP]?1:0)<<0)| // PARTY - Show attack cursor on non-party members (PvP)
+	WBUFL(buf,4) = ((mapdata->flag[MF_PVP]?1:0 || (bl->type == BL_PC && ((TBL_PC *)bl)->duel_group > 0))<<0)| // PARTY - Show attack cursor on non-party members (PvP)
 		((mapdata->flag[MF_BATTLEGROUND] || mapdata_flag_gvg2(mapdata)?1:0)<<1)|// GUILD - Show attack cursor on non-guild members (GvG)
 		((mapdata->flag[MF_BATTLEGROUND] || mapdata_flag_gvg2(mapdata)?1:0)<<2)|// SIEGE - Show emblem over characters heads when in GvG (WoE castle)
 		((mapdata->flag[MF_NOMINEEFFECT] || !mapdata_flag_gvg2(mapdata)?0:1)<<3)| // USE_SIMPLE_EFFECT - Automatically enable /mineffect