Hotfix for warning in dim.h
Hotfix for warning in dim.h

danielhers/dynet,clab/dynet,shuheik/dynet,clab/cnn,danielhers/dynet,chunyang-wen/dynet,xunzhang/dynet,chunyang-wen/dynet,shuheik/dynet,clab/dynet,chunyang-wen/dynet,clab/dynet,xunzhang/dynet,clab/dynet,clab/dynet,shuheik/dynet,danielhers/dynet,shuheik/dynet,xunzhang/dynet,shuheik/dynet,clab/dynet,danielhers/dynet,xunzhang/dynet,shuheik/dynet,danielhers/dynet,shuheik/dynet,clab/cnn,danielhers/dynet,danielhers/dynet,chunyang-wen/dynet,clab/cnn,clab/dynet