Fix SparseToDenseMask for int64 indices
Fix SparseToDenseMask for int64 indices

Summary: that what made tests fail :)

Reviewed By: xianjiec

Differential Revision: D6067037

fbshipit-source-id: 0194f082feed87b0502170683c6773e07db3ff44

xzturn/caffe2,Yangqing/caffe2,sf-wind/caffe2,sf-wind/caffe2,sf-wind/caffe2,caffe2/caffe2,Yangqing/caffe2,Yangqing/caffe2,davinwang/caffe2,davinwang/caffe2,sf-wind/caffe2,Yangqing/caffe2,davinwang/caffe2,xzturn/caffe2,pietern/caffe2,xzturn/caffe2,Yangqing/caffe2,pietern/caffe2,xzturn/caffe2,pietern/caffe2,davinwang/caffe2,xzturn/caffe2,sf-wind/caffe2,pietern/caffe2,pietern/caffe2,davinwang/caffe2