Remove negative sum check in entropy_optimizer
Remove negative sum check in entropy_optimizer

csum[] adds an extra +1 with every element. The only way for sum to be
<= 0 is if (a) there were no elements (and hence no loop, and no
cdf[0]), or (b) some of those elements were negative.

Change-Id: I727193957753a794b8bb057ab24c7b1e5d276478

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom