Nil error for something I cannot track down

[myrroddin]

Attached is a zip of my WIP of RepByZone, as copying my Lua code will take up a lot of space in a thread. I do understand the error, but cannot explain what is causing it to happen. The variable that should have data is on line 141 of Core-Retail.lua, in the Onitialize function, and refreshed on line 6 of Options.lua just in case the user has changed something. Why Options.lua cannot see that variable, I don't know.

I need fresh eyes, methinks. The error dump is below.

1x RepByZone\Options-Options.lua:77: bad argument #1 to 'format' (string expected, got nil)
[string "=[C]"]: in function `format'
[string "@RepByZone\Options-Options.lua"]:77: in function `member'
[string "@Ace3\AceConfig-3.0-3\AceConfigDialog-3.0\AceConfigDialog-3.0-81.lua"]:221: in function <...nfig-3.0\AceConfigDialog-3.0\AceConfigDialog-3.0.lua:169>
[string "@Ace3\AceConfig-3.0-3\AceConfigDialog-3.0\AceConfigDialog-3.0-81.lua"]:1211: in function <...nfig-3.0\AceConfigDialog-3.0\AceConfigDialog-3.0.lua:1121>
[string "@Ace3\AceConfig-3.0-3\AceConfigDialog-3.0\AceConfigDialog-3.0-81.lua"]:1652: in function `FeedGroup'
[string "@Ace3\AceConfig-3.0-3\AceConfigDialog-3.0\AceConfigDialog-3.0-81.lua"]:1577: in function <...nfig-3.0\AceConfigDialog-3.0\AceConfigDialog-3.0.lua:1561>
[string "=[C]"]: ?
[string "@Ace3\AceGUI-3.0\AceGUI-3.0-41.lua"]:72: in function <Ace3\AceGUI-3.0\AceGUI-3.0.lua:70>
[string "@Ace3\AceGUI-3.0\AceGUI-3.0-41.lua"]:306: in function `Fire'
[string "@Ace3\AceGUI-3.0-41\widgets\AceGUIContainer-TabGroup.lua"]:156: in function `SelectTab'
[string "@Ace3\AceConfig-3.0-3\AceConfigDialog-3.0\AceConfigDialog-3.0-81.lua"]:1688: in function `FeedGroup'
[string "@Ace3\AceConfig-3.0-3\AceConfigDialog-3.0\AceConfigDialog-3.0-81.lua"]:1932: in function `Open'
[string "@RepByZone\Core-Retail.lua"]:196: in function `?'
[string "@Ace3\AceConsole-3.0\AceConsole-3.0-7.lua"]:94: in function `?'
[string "@FrameXML\ChatFrame.lua"]:5094: in function `ChatEdit_ParseText'
[string "@FrameXML\ChatFrame.lua"]:4758: in function `ChatEdit_SendText'
[string "@FrameXML\ChatFrame.lua"]:4794: in function <FrameXML\ChatFrame.lua:4790>
[string "=[C]"]: in function `ChatEdit_OnEnterPressed'
[string "*:OnEnterPressed"]:1: in function <[string "*:OnEnterPressed"]:1>