Thread:Extension talk:Scribunto/Lua error in Module:List

I'm running MW 1.22.6 and Scribunto REL1_22 and I'm receiving the following error from the Template:Navbox I imported from Wikipedia:

Lua error in Module:List at line 110: attempt to index field 'html' (a nil value). Backtrace: Module:List:110: in function "renderList" Module:List:181: ? (tail call): ? mw.lua:553: ? [C]: in function "getAllExpandedArguments" mw.lua:283: ? [C]: in function "iterator" Module:Arguments:133: in function "mergeArgs" Module:Arguments:223: ? [C]: in function "pairs" Module:Message_box:182: in function "removeBlankArgs" Module:Message_box:624: ? (tail call): ? mw.lua:553: ? [C]: in function "getExpandedArgument" mw.lua:264: ? Module:Arguments:177: ? Module:Documentation:648: in function "_content" Module:Documentation:141: ? (tail call): ? mw.lua:553: ?

Thanks.