I'm still finding typos in the source code. I propose that you keep this PR open prior ro relaese and then merge so that if I find other typos in the meantime they will be part this release.
Part::FaceMaker::ConstructFromType() could return null pointer if
abstract class type is supplied.
Here, it is fixed by checking for null pointer in facemaker itself,
rather than in every place ConstructFromType is being used.