small fix for pointer initialization.
small fix for pointer initialization.

Summary: A bit safer, and also suppresses compiler warning.

Reviewed By: bddppq

Differential Revision: D5803080

fbshipit-source-id: d8c782c936a8fdaded4ae209b212378e78606ffb

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