Remove enforce to have tensor data_ when sharing tensors
Remove enforce to have tensor data_ when sharing tensors

Summary: We don't need this enforce since we already allow raw_mutable_data to return nullptr, we should be able to share meta for tensors even without data

Reviewed By: Yangqing, kennyhorror

Differential Revision: D4439138

fbshipit-source-id: 0e81bef3054fe2f9720efd5002418eac7a2b6c08

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