Throws exception if added item is detected as a duplicate - fixes #364
Throws exception if added item is detected as a duplicate - fixes #364

nuller1joe/SteamBot,niachris/SteamBotNew,23RDGit/CSGOWinBig-SteamBot,BlueRaja/SteamBot,zigagrcar/SteamTradeOffersBot,ChalkyBrush/SteamBots,wqbill/SteamBot,Moondarker/CSGOWinBig-SteamBot,JackHarknes/Bot1,icodingforfood/SteamBot,trervorx/SteamBot,23RDGit/CSGOWinBig-SteamBot,MattrAus/SteamBot,MadBender/SteamBot,ChalkyBrush/SteamBots,BuzzyOG/CSGOWinBig-SteamBot,Wendt9222/SteamBot-1,Bottswana/SteamBot,avoak/SteamBot,TheRod1990/SteamBot,martingabriel/SteamBot,GoeGaming/SteamBot,waylaidwanderer/SteamTradeOffersBot,alanfort/CSGOWinBig-SteamBot,tarun200897/SteamBot,stackia/SteamBot,Alex-Nabu/CSGOWinBig-SteamBot,Schwehn42/SteamBot,MattrAus/SteamBot,Murzyneczka/CSGOWinBig-SteamBot,GAMELASTER/SteamBot,wowzone/gamerpro,TheRod1990/SteamBot,alanfort/CSGOWinBig-SteamBot,BuzzyOG/CSGOWinBig-SteamBot,martingabriel/SteamBot,GAMELASTER/SteamBot,novasdream/SteamBot,zigagrcar/SteamTradeOffersBot,ztizzlegaming/CSGOWinBig-SteamBot,Schwehn42/SteamBot,MadBender/SteamBot,fjch1997/SteamBot,fjch1997/SteamBot,stigping/SteamBot,JackHarknes/Bot1,wowzone/gamerpro,icodingforfood/SteamBot,stackia/SteamBot,terryhau/SteamBot,Bottswana/SteamBot,Moondarker/CSGOWinBig-SteamBot,tarun200897/SteamBot,stigping/SteamBot,StormReaper/SteamBot,terryhau/SteamBot,xversial/SteamBot,ztizzlegaming/CSGOWinBig-SteamBot,Jessecar96/SteamBot,trervorx/SteamBot,xversial/SteamBot,niachris/SteamBotNew,JackHarknes/Bot1,GoeGaming/SteamBot,Wendt9222/SteamBot-1,Banana23/Tryout,Murzyneczka/CSGOWinBig-SteamBot,nuller1joe/SteamBot,novasdream/SteamBot,wqbill/SteamBot,Banana23/Tryout,Alex-Nabu/CSGOWinBig-SteamBot,avoak/SteamBot,StormReaper/SteamBot