Handle nomask result in cluster_prediction

[RomRoc]

Thanks for your interesting repo, it inspired me a lot in my projects.
I think there is a small issue in cluster_prediction function:

data_science_bowl_2018/codes/predict.py

Line 232 in 0a6d0ed

if np.max(overlaps[mm]) > 0.1:

In my project I get error when overlaps[mm] is empty.
I modified line in this way to solve it:
if overlaps[mm].size != 0 and np.max(overlaps[mm]) > 0.1: