Allow no-bias MKLDNN Linear call (#43703)
Summary:
MKLDNN linear incorrectly assumes that bias is defined and will fail for no-bias calls.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43703
Reviewed By: glaringlee
Differential Revision: D23373182
Pulled By: bwasti
fbshipit-source-id: 1e817674838a07d237c02eebe235c386cf5b191e
