Strange error

[dovanchan]

When I try to transfer a phoho with this command:
DOVANtekiMacBook-Pro:chainer-neural-style DOVAN$ time python src/run.py -c /Users/DOVAN/Desktop/model.png -s /Users/DOVAN/Desktop/111.png -o /Users/DOVAN/Desktop/chai/modelcat -g -1 --match_color_histogram

loading content image completed
/Users/DOVAN/deeprely/chainer-neural-style/src/util.py:113: RuntimeWarning: invalid value encountered in sqrt
b_sigma = v.dot(np.diag(d ** 0.5)).dot(v.T)
loading style image completed
loading neural network model completed
/Users/DOVAN/anaconda2/lib/python2.7/site-packages/chainer/functions/activation/relu.py:44: RuntimeWarning: invalid value encountered in greater
return utils.force_array(gy[0] * (x[0] > 0)),
epoch 100 done
losses:
content_4_2: nan
style_1_2 : nan
style_2_2 : nan
style_3_2 : nan
style_4_2 : nan
tv : nan
epoch 200 done
losses:
content_4_2: nan
style_1_2 : nan
style_2_2 : nan
style_3_2 : nan
style_4_2 : nan
tv : nan
epoch 300 done
losses:
content_4_2: nan
style_1_2 : nan
style_2_2 : nan
style_3_2 : nan
style_4_2 : nan
tv : nan

Why all of loss are nan ~;
It's a bug in --match_color_histogram ?
(without this match_color,everything is fine)

[dsanno]

It seems that gray scale image causes the problem.
I fixed it in aecabb6, and can you try again?
If the same problem occurs, please tell me your style image.
I think this problem depends on style image.