Problem with mapper

[fanlamda]

I changed a few things in mapper.lua to adapt to Chinese study, but it comes error like
/home/fanl/torch/install/share/lua/5.1/threads/threads.lua:183: [thread 1 callback] ./Mapper.lua:23: bad argument #1 to 'lower' (string expected, got nil)
stack traceback:
[C]: in function 'lower'
./Mapper.lua:23: in function 'encodeString'
./Loader.lua:92: in function <./Loader.lua:62>

[Sean Naren]

So it seems like the line going into the mapper is nil for some odd reason, is there any way that a nil could've been inserted into the LMDB, or the label is nil?

[fanlamda]

There was a mistake in label when I dealt with the label. Now it works