WoWInterface - Quest Item BAR setbackdrop fix request

I had a version of this addon working till last patch 9.01 the unique thing about Quest Item bar was ability to drag and drop any Item I need to monitor on the fly

its now giving mainly setback error that is causing other errors on Core.lua

would be great is someone could guide on how to fix the setback error

Error 1) Original lines

87 local overlay = CreateFrame("Frame", f:GetName() .. "Overlay", f)
88 f.overlay = overlay
89 overlay:EnableMouse(true)
90 overlay:SetBackdrop({
91 bgFile = "Interface\\Tooltips\\UI-Tooltip-Background",
92 tile = true,
93 tileSize = 16,
94 --edgeFile = "Interface\\Tooltips\\UI-Tooltip-Border",
95 --edgeSize = 16,
96 --insets = {left = 3, right = 3, top = 3, bottom = 3}
97 })
98 overlay:SetBackdropColor(0,0,0,1)
99 overlay:SetBackdropBorderColor(0.3,0.3,0.3,1)

Error 1 Bug in game :

1x QuestItemBar\Core.lua:90: attempt to call method 'SetBackdrop' (a nil value)
[string "@QuestItemBar\Core.lua"]:90: in function `CreateAnchor'
[string "@QuestItemBar\Core.lua"]:360: in function <QuestItemBar\Core.lua:354>
[string "=[C]"]: ?
[string "@ElvUI\Libraries\Ace3\AceAddon-3.0\AceAddon-3.0-13.lua"]:70: in function <...s\ElvUI\Libraries\Ace3\AceAddon-3.0\AceAddon-3.0.lua:65>
[string "@ElvUI\Libraries\Ace3\AceAddon-3.0\AceAddon-3.0-13.lua"]:498: in function `InitializeAddon'
[string "@ElvUI\Libraries\Ace3\AceAddon-3.0\AceAddon-3.0-13.lua"]:623: in function <...s\ElvUI\Libraries\Ace3\AceAddon-3.0\AceAddon-3.0.lua:615>