Core/Items: Fix item sell price not scaling with item level

Port From (https://github.com/TrinityCore/TrinityCore/commit/500301b96256792357b13ef78d7e1836028cff26)

Source/Game/Entities/Item/Item.cs

@@ -1754,7 +1754,7 @@ namespace Game.Entities
                 typeFactor = weaponPrice.Data;
             }
 
-            standardPrice = false;
+            standardPrice = true;
             return (uint)(proto.GetPriceVariance() * typeFactor * baseFactor * qualityFactor * proto.GetPriceRandomValue());
         }
 

Source/Game/Entities/Player/Player.Items.cs

@@ -3039,11 +3039,7 @@ namespace Game.Entities
                 uint eslot = slot - InventorySlots.BuyBackStart;
 
                 SetInvSlot(slot, pItem.GetGUID());
-                ItemTemplate proto = pItem.GetTemplate();
+                SetBuybackPrice(eslot, pItem.GetSellPrice(this) * pItem.GetCount());
-                if (proto != null)
-                    SetBuybackPrice(eslot, proto.GetSellPrice() * pItem.GetCount());
-                else
-                    SetBuybackPrice(eslot, 0);
 
                 SetBuybackTimestamp(eslot, etime);
 

Source/Game/Handlers/ItemHandler.cs

@@ -429,12 +429,16 @@ namespace Game
                     }
                 }
 
-                ItemTemplate pProto = pItem.GetTemplate();
+                uint sellPrice = pItem.GetSellPrice(_player);
-                if (pProto != null)
+                if (sellPrice > 0)
                 {
-                    if (pProto.GetSellPrice() > 0)
+                    ulong money = sellPrice * packet.Amount;
+
+                    if (money > uint.MaxValue) // ensure sell price * amount doesn't overflow buyback price
                     {
-                        ulong money = pProto.GetSellPrice() * packet.Amount;
+                        _player.SendSellError(SellResult.CantSellItem, creature, packet.ItemGUID);
+                        return;
+                    }
 
                     if (!_player.ModifyMoney((long)money)) // ensure player doesn't exceed gold limit
                     {
@@ -477,8 +481,7 @@ namespace Game
                     pl.SendSellError(SellResult.CantSellItem, creature, packet.ItemGUID);
                 return;
             }
-            }
+            pl.SendSellError(SellResult.CantFindItem, creature, packet.ItemGUID);
-            pl.SendSellError(SellResult.CantSellItem, creature, packet.ItemGUID);
             return;
         }