2_supervised error

[Carles Gelada]

this is the errror:

lua:78: attempt to index field 'file' (a nil value)
stack traceback:
    /home/ubuntu/torch/install/share/lua/5.1/optim/Logger.lua:78: in function 'add'
    4_train.lua:197: in function 'train'
    doall.lua:77: in main chunk
    [C]: in function 'dofile'
    ...untu/torch/install/lib/luarocks/rocks/trepl/scm-1/bin/th:131: in main chunk
    [C]: at 0x00406670