Fixed warning
Fixed warning


Former-commit-id: 907ec981f2809e3e45e7b4ca91b6a7c33c390c17
xunzhang/dynet,danielhers/dynet,shuheik/dynet,chunyang-wen/dynet,xunzhang/dynet,clab/dynet,shuheik/dynet,shuheik/dynet,clab/cnn,clab/dynet,clab/dynet,shuheik/dynet,danielhers/dynet,danielhers/dynet,chunyang-wen/dynet,danielhers/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,clab/cnn,clab/dynet,danielhers/dynet,shuheik/dynet,clab/cnn,danielhers/dynet,chunyang-wen/dynet,chunyang-wen/dynet,shuheik/dynet,xunzhang/dynet,clab/dynet,clab/dynet,xunzhang/dynet