Fix SparseLengthSum undeclared schema
Fix SparseLengthSum undeclared schema

Differential Revision: D5495760

fbshipit-source-id: a2c9e6204021687f6df830ea2bfbe355bfc888be

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