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

Regression by commit 81243ea

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

lib/Inline/Perl5.pm6

@@ -939,8 +939,8 @@ method BUILD(*%args) {
     else {
         my @args = @*ARGS;
         $!p5 = p5_init_perl(@args.elems + 4, CArray[Str].new('', '-e', '0', '--', |@args));
+        X::Inline::Perl5::NoMultiplicity.new.throw unless $!p5.defined;
     }
-    X::Inline::Perl5::NoMultiplicity.new.throw unless $!p5.defined;
 
     &!call_method = sub (Int $index, Str $name, Int $context, Pointer $args, Pointer $err) returns Pointer {
         my $p6obj = $objects.get($index);