* fix overflow by int32 mul test=develop

* fix reference nullptr

* fix codestyle test=develop

* modify to point in ContextProjectFunctor test=develop

* modify to point in ContextProjectFunctor test=develop

* modify . to -> test=develop

* refine embedding padding_idx doc test=develop

* fix math:padding_idx preview bug test=develop

* modify API.spec test=develop

* fix spell error test=develop

* refine dtype parm desc test=develop