Strange Talent Frame Error.

[kaytotes]

One of my users has reported an error that I can't seem to be able to track down. It seems to be pointing at the Blizzard Talent Frame but I'm in no way hooking into it and I think (hope) I'm largely taint free. Instead of pastebin I hope its okay to point directly at my github for code. It appears to occur with every other addon disabled besides my BlizzImp.

https://github.com/uutfboomheadshot/...aster/BlizzImp

This is the full error :

Message: ...rface\AddOns\Blizzard_TalentUI\Blizzard_TalentUI.lua:717: attempt to concatenate local 'tier' (a nil value)
Time: 12/01/14 19:36:07
Count: 2
Stack: ...rface\AddOns\Blizzard_TalentUI\Blizzard_TalentUI.lua:717: in function `PlayerTalentFrame_SelectTalent'
...rface\AddOns\Blizzard_TalentUI\Blizzard_TalentUI.lua:40: in function `OnAccept'
Interface\FrameXML\StaticPopup.lua:3945: in function `StaticPopup_OnClick'
[string "*:OnClick"]:1: in function <[string "*:OnClick"]:1>

Locals: tier = nil
id = nil
(*temporary) = PlayerTalentFrameTalents {
0 = <userdata>
clearInfo = PlayerTalentFrameTalentsClearInfoFrame {
}
tier2 = PlayerTalentFrameTalentsTalentRow2 {
}
unspentText = <unnamed> {
}
talentGroup = 2
tier3 = PlayerTalentFrameTalentsTalentRow3 {
}
summariesShownWhenNoPrimary = true
learnButton = PlayerTalentFrameTalentsLearnButton {
}
tier5 = PlayerTalentFrameTalentsTalentRow5 {
}
MainHelpButton = PlayerTalentFrameTalentsTutorialButton {
}
tier7 = PlayerTalentFrameTalentsTalentRow7 {
}
tier1 = PlayerTalentFrameTalentsTalentRow1 {
}
tier4 = PlayerTalentFrameTalentsTalentRow4 {
}
bg = PlayerTalentFrameTalentsBg {
}
tier6 = PlayerTalentFrameTalentsTalentRow6 {
}
}
(*temporary) = "tier"
(*temporary) = nil
(*temporary) = nil
(*temporary) = "attempt to concatenate local 'tier' (a nil value)"