Can anyone help me with this.

Whenever I call an infobox template that I created from anywhere else on my wiki I get a Lua script error. The templates were fine for over a year until someone tried to import a page (which was later deleted) the error however did you not go away.

What does this error mean?

Lua error in Module:Infobox at line 229: attempt to index field 'html' (a nil value).

Backtrace:

(tail call): ?
Module:Infobox:229: ?
(tail call): ?
mw.lua:553: ?
(tail call): ?
[C]: in function "xpcall"
MWServer.lua:73: in function "handleCall"
MWServer.lua:266: in function "dispatch"
MWServer.lua:33: in function "execute"
mw_main.lua:7: in main chunk
[C]: ?