Issue with texture widget on Shadowlands Beta with Covenant MissionUI

[liquidbase]

Prerequisites

• [ ] Are you running the latest release of Aurora? If you're using the Twitch updater, make sure the release type is set to "Release" unless told otherwise.
• [X] Did you perform a cursory search to see if your bug or enhancement is already reported?

Description

Opening Missions-UI produces the an error with the latest alpha build from GitHub on Shadowlands Beta

Steps to Reproduce

1. Opening covenant mission UI

Message: Interface\AddOns\Aurora\Skin\api.lua:215: texture widget expected, got nil
Time: Sat Sep 26 11:47:06 2020
Count: 1
Stack: Interface\AddOns\Aurora\Skin\api.lua:215: texture widget expected, got nil
[string "=[C]"]: in function `assert'
[string "@Interface\AddOns\Aurora\Skin\api.lua"]:215: in function `SetTexture'
[string "@Interface\AddOns\Aurora\Skin\backdrop.lua"]:223: in function `ApplyBackdrop'
[string "@Interface\SharedXML\Backdrop.lua"]:394: in function <Interface\SharedXML\Backdrop.lua:382>
[string "=(tail call)"]: ?
[string "@Interface\AddOns\Aurora\Skin\backdrop.lua"]:582: in function `CreateBackdrop'
[string "@Interface\AddOns\Aurora\aurora.lua"]:134: in function `SetBackdrop'
[string "@Interface\AddOns\Aurora\Skin\Retail\AddOns\Blizzard_GarrisonUI.lua"]:191: in function `?'
[string "@Interface\AddOns\Aurora\Skin\Retail\SharedXML\HybridScrollFrame.lua"]:19: in function <...s\Aurora\Skin\Retail\SharedXML\HybridScrollFrame.lua:12>
[string "=[C]"]: in function `HybridScrollFrame_CreateButtons'
[string "@Interface\AddOns\Blizzard_GarrisonUI\Blizzard_GarrisonMissionUI.lua"]:22: in function `SetupMissionList'
[string "@Interface\AddOns\Blizzard_GarrisonUI\Blizzard_GarrisonMissionUI.lua"]:37: in function <...s\Blizzard_GarrisonUI\Blizzard_GarrisonMissionUI.lua:28>
[string "=[C]"]: in function `LoadAddOn'
[string "@Interface\FrameXML\UIParent.lua"]:494: in function `UIParentLoadAddOn'
[string "@Interface\FrameXML\UIParent.lua"]:680: in function `Garrison_LoadUI'
[string "@Interface\FrameXML\UIParent.lua"]:1923: in function <Interface\FrameXML\UIParent.lua:1243>

Locals: (*temporary) = false
(*temporary) = "texture widget expected, got nil"