handle empty inputs to SparseLengthsMean correctly (#15389)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15389
SparseLengthsMean was generating uninitialized data for empty inputs (lengths == 0). We should return zeros.
The unit tests were also not covering this special case which is fixed by this diff.
Reviewed By: salexspb
Differential Revision: D13515970
fbshipit-source-id: 3c35265638f64f13f0262cee930c94f8628005da
