if CPAN::Meta->load_file fails, create new CPAN::Meta

If doing CPAN::Meta->load_file for META.json/META.yml fails, then we don't gather any provides at all, causing indexing failures in carton. This failure can be seen in WWW::Mechanize::GZip (0.12), which has no META.json and an empty META.yml file, and in MooseX::Types::DateTime::MoreCoercions (0.11).