Various fixes for building with new compilers by starseeker · Pull Request #466 · stepcode/stepcode

Co-authored-by: starseeker <238416+starseeker@users.noreply.github.com>

Co-authored-by: starseeker <238416+starseeker@users.noreply.github.com>

…arations

Co-authored-by: starseeker <238416+starseeker@users.noreply.github.com>

Improves error handling in STEPattributeList operator[] - return an
error attribute and set error state rather than trying to rely on
crashing via a NULL deference.  That's undefined behavior, so it
was not guaranteed - this requires the calling code to check the
return, but is *much* cleaner.

Co-authored-by: starseeker <238416+starseeker@users.noreply.github.com>

Co-authored-by: starseeker <238416+starseeker@users.noreply.github.com>