Fixed missing initialization in hinge loss
Fixed missing initialization in hinge loss


Former-commit-id: 737deb7f8e083f6cba6e0d3fdde8f91faa0cbf7c
danielhers/dynet,danielhers/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,clab/dynet,shuheik/dynet,chunyang-wen/dynet,shuheik/dynet,clab/cnn,xunzhang/dynet,chunyang-wen/dynet,clab/cnn,chunyang-wen/dynet,clab/cnn,xunzhang/dynet,shuheik/dynet,xunzhang/dynet,danielhers/dynet,shuheik/dynet,danielhers/dynet,danielhers/dynet,clab/dynet,clab/dynet,shuheik/dynet,clab/dynet,chunyang-wen/dynet,danielhers/dynet,clab/dynet,xunzhang/dynet,clab/dynet,shuheik/dynet