Message: ...ns\iMoney\Libs\iLib\Libs\LibQTip-1.0\LibQTip-1.0.lua:519: attempt to call method 'SetBackdrop' (a nil value)
Time: Wed May 19 20:17:51 2021
Count: 1
Stack: ...ns\iMoney\Libs\iLib\Libs\LibQTip-1.0\LibQTip-1.0.lua:519: attempt to call method 'SetBackdrop' (a nil value)
[string "@interface\AddOns\iMoney\Libs\iLib\Libs\LibQTip-1.0\LibQTip-1.0.lua"]:519: in function <...ns\iMoney\Libs\iLib\Libs\LibQTip-1.0\LibQTip-1.0.lua:513>
[string "@interface\AddOns\iMoney\Libs\iLib\Libs\LibQTip-1.0\LibQTip-1.0.lua"]:126: in function <...ns\iMoney\Libs\iLib\Libs\LibQTip-1.0\LibQTip-1.0.lua:117>
[string "=(tail call)"]: ?
[string "@interface\AddOns\iMoney\Libs\iLib\iLib.lua"]:486: in function <Interface\AddOns\iMoney\Libs\iLib\iLib.lua:479>
[string "@interface\AddOns\iMoney\Libs\iLib\iLib.lua"]:518: in function `GetTooltip'
[string "@interface\AddOns\iMoney\iMoney.lua"]:69: in function <Interface\AddOns\iMoney\iMoney.lua:62>

I fixed this by correcting the issue within the LibQtip file. Replace the -- line with the ++ line. Do not incluce the --, ++, line number or colon:

iMoney\Libs\iLib\Libs\LibQTip-1.0\LibQTip-1.0.lua
--40: lib.frameMetatable = lib.frameMetatable or {__index = CreateFrame("Frame")}
++40: lib.frameMetatable = lib.frameMetatable or {__index = CreateFrame("Frame", BackdropTemplateMixin and "BackdropTemplate")}

--70: local highlightFrame = CreateFrame("Frame", nil, UIParent)
++70: local highlightFrame = CreateFrame("Frame", nil, UIParent, BackdropTemplateMixin and "BackdropTemplate")

--171: local highlightFrame = CreateFrame("Frame", nil, UIParent)
++171: local highlightFrame = CreateFrame("Frame", nil, UIParent, BackdropTemplateMixin and "BackdropTemplate")

--196: lib.layoutCleaner = lib.layoutCleaner or CreateFrame("Frame")
++196: lib.layoutCleaner = lib.layoutCleaner or CreateFrame("Frame", BackdropTemplateMixin and "BackdropTemplate")

--225: cell = setmetatable(CreateFrame("Frame", nil, UIParent), self.cellMetatable)
++225: cell = setmetatable(CreateFrame("Frame", nil, UIParent, BackdropTemplateMixin and "BackdropTemplate"), self.cellMetatable)

--364: tooltip = CreateFrame("Frame", nil, UIParent)
++364: tooltip = CreateFrame("Frame", nil, UIParent, BackdropTemplateMixin and "BackdropTemplate")

--366: local scrollFrame = CreateFrame("ScrollFrame", nil, tooltip)
++366: local scrollFrame = CreateFrame("ScrollFrame", nil, tooltip, BackdropTemplateMixin and "BackdropTemplate")

--373: local scrollChild = CreateFrame("Frame", nil, tooltip.scrollFrame)
++373: local scrollChild = CreateFrame("Frame", nil, tooltip.scrollFrame, BackdropTemplateMixin and "BackdropTemplate")

--735: local slider = CreateFrame("Slider", nil, self)
++735: local slider = CreateFrame("Slider", nil, self, BackdropTemplateMixin and "BackdropTemplate")

I fixed this by correcting the issue within the LibQtip file. Replace the -- line with the ++ line. Do not incluce the --, ++, line number or colon:

iMoney\Libs\iLib\Libs\LibQTip-1.0\LibQTip-1.0.lua
--40: lib.frameMetatable = lib.frameMetatable or {__index = CreateFrame("Frame")}
++40: lib.frameMetatable = lib.frameMetatable or {__index = CreateFrame("Frame", BackdropTemplateMixin and "BackdropTemplate")}

--70: local highlightFrame = CreateFrame("Frame", nil, UIParent)
++70: local highlightFrame = CreateFrame("Frame", nil, UIParent, BackdropTemplateMixin and "BackdropTemplate")

--171: local highlightFrame = CreateFrame("Frame", nil, UIParent)
++171: local highlightFrame = CreateFrame("Frame", nil, UIParent, BackdropTemplateMixin and "BackdropTemplate")

--196: lib.layoutCleaner = lib.layoutCleaner or CreateFrame("Frame")
++196: lib.layoutCleaner = lib.layoutCleaner or CreateFrame("Frame", BackdropTemplateMixin and "BackdropTemplate")

--225: cell = setmetatable(CreateFrame("Frame", nil, UIParent), self.cellMetatable)
++225: cell = setmetatable(CreateFrame("Frame", nil, UIParent, BackdropTemplateMixin and "BackdropTemplate"), self.cellMetatable)

--364: tooltip = CreateFrame("Frame", nil, UIParent)
++364: tooltip = CreateFrame("Frame", nil, UIParent, BackdropTemplateMixin and "BackdropTemplate")

--366: local scrollFrame = CreateFrame("ScrollFrame", nil, tooltip)
++366: local scrollFrame = CreateFrame("ScrollFrame", nil, tooltip, BackdropTemplateMixin and "BackdropTemplate")

--373: local scrollChild = CreateFrame("Frame", nil, tooltip.scrollFrame)
++373: local scrollChild = CreateFrame("Frame", nil, tooltip.scrollFrame, BackdropTemplateMixin and "BackdropTemplate")

--735: local slider = CreateFrame("Slider", nil, self)
++735: local slider = CreateFrame("Slider", nil, self, BackdropTemplateMixin and "BackdropTemplate")

Your Fix wont work for me. Getting a new error T.T

Just update the LibQtip, you can get it over at https://www.curseforge.com/wow/addons/libqtip-1-0/files/3092811