evaluate_model error of 'bad argument'

Hello,
I get error when running 'evaluate_model.lua'. It appears with both VG 1.0 and 1.2:
`THNN.lua:110: bad argument #8 to 'v' (cannot convert 'nil' to 'int64_t')`

Any suggestions are highly appreciated!

## Steps
1. Necessary packages are installed as from the [Installation guideline](https://github.com/jcjohnson/densecap/blob/master/doc/INSTALL.md)

2. Image preprocessing succeeds with
`python preprocess.py --region_data ~/data/VG2015/region_descriptions.json --image_dir ~/data/VG2015/VG_100K --image_size 720 --split_json info/densecap_splits.json --json_output ~/data/VG2015/VG_100k_sorted.json --h5_output ~/data/VG2015/VG_100k_sorted.hdf5 --num_workers 6`

3. Error comes with
`th evaluate_model.lua -checkpoint data/models/densecap/densecap-pretrained-vgg16.t7 -split val -gpu 0 -use_cudnn 0 -num_proposals 300 -data_h5 ~/data/VG2015/VG_100k_sorted.hdf5 -data_json ~/data/VG2015/VG_100k_sorted.json`

Loaded model
Using dtype "torch.CudaTensor"
DataLoader loading json file: /home/sujing/data/VG2015/VG_100k_sorted.json
DataLoader loading h5 file: /home/sujing/data/VG2015/VG_100k_sorted.hdf5
reading box_to_img
reading boxes
reading image_heights
reading image_widths
reading img_to_first_box
reading img_to_last_box
reading labels
reading lengths
reading original_heights
reading original_widths
reading split
assigned 77396/5000/5000 images to train/val/test.
initialized DataLoader:
#images: 87396, #regions: 4062806, sequence max length: 15
using split 1
/home/sujing/workspace/torch/install/bin/luajit: ...g/workspace/torch/install/share/lua/5.1/nn/Container.lua:67:
In 3 module of nn.Sequential:
...sujing/workspace/torch/install/share/lua/5.1/nn/THNN.lua:110: bad argument #8 to 'v' (cannot convert 'nil' to 'int64_t')
stack traceback:
[C]: in function 'v'
...sujing/workspace/torch/install/share/lua/5.1/nn/THNN.lua:110: in function 'ClassNLLCriterion_updateOutput'
...ace/torch/install/share/lua/5.1/nn/ClassNLLCriterion.lua:41: in function 'updateOutput'
./densecap/modules/OurCrossEntropyCriterion.lua:19: in function 'forward'
./densecap/LocalizationLayer.lua:466: in function 'f'
./densecap/LocalizationLayer.lua:228: in function 'timeit'
./densecap/LocalizationLayer.lua:455: in function <./densecap/LocalizationLayer.lua:383>
[C]: in function 'xpcall'
...g/workspace/torch/install/share/lua/5.1/nn/Container.lua:63: in function 'rethrowErrors'
.../workspace/torch/install/share/lua/5.1/nn/Sequential.lua:44: in function 'forward'
./densecap/DenseCapModel.lua:253: in function 'forward'
./densecap/DenseCapModel.lua:406: in function 'forward_backward'
./eval/eval_utils.lua:58: in function 'eval_split'
evaluate_model.lua:63: in main chunk
[C]: in function 'dofile'
...pace/torch/install/lib/luarocks/rocks/trepl/scm-1/bin/th:150: in main chunk
[C]: at 0x00405d50