I'll fix it on my end, but it's generally bad practice by other addon authors to use plain numbers as frame names. In this case, the offending title is ArtifactTab.
Also, please use spoiler for massive Lua error outputs.
Would be great if you exposed your API to get the best item reward index when choosing items. I'm hosting an addon called Immersion which completely replaces the quest frame. As such, it would be great to be able to query for item recommendations without you hardcoding support for other addons on your end.