* fix nas (#553)

* fix when lambda_distill is None in ofa (#550)

* fix

* fix when lambda is None

* fix when the task is mnli (#540)

* fix

* fix when mnli

* Fix ofa (#536)

* fix

* fix embedding
Co-authored-by: NBai Yifan <me@ethanbai.com>
Co-authored-by: NBai Yifan <me@ethanbai.com>