Fix bogus error in Inline::Perl6 on perl without MULTIPLICITY
Fix bogus error in Inline::Perl6 on perl without MULTIPLICITY

Regression by commit 81243ea6518267be718bf5e092e9c09b9a36f281

Thanks to Ævar for the report!
Fixes Inline::Perl6 GH #2

niner/Inline-Perl5,niner/Inline-Perl5