flypage SpecialSub fix for non-existent SKUs.

If the flypge SpecialSub returned a non-existent SKU then a blank flypage would
be displayed (with no data).  This is now fixed so that there is no difference
to what happens without a SpecialSub.

WHATSNEW-5.7

@@ -127,6 +127,10 @@ Core
   because Getopt::Long ignores option case by default.  This fixes the problem
   by passing the no_ignore_case config parameter to Getopt::Long.
 
+* If the flypge SpecialSub returned a non-existent SKU then a blank flypage
+  would be displayed (with no data).  This is now fixed so that there is no
+  difference to what happens without a SpecialSub.
+
 Payment
 -------
 

lib/Vend/Interpolate.pm

@@ -4956,12 +4956,12 @@ sub fly_page {
 		my $sub = $Vend::Cfg->{Sub}{$subname} || $Global::GlobalSub->{$subname}; 
 		$listref = $sub->($code);
 		$listref = { mv_results => [[$listref]] } unless ref($listref);
-		$base = $listref;
+		$code = $listref->{mv_results}[0][0] if defined $listref->{mv_results}[0][0];
 	}
 	else {
-		$base = product_code_exists_ref($code);
 		$listref = {mv_results => [[$code]]};
 	}
+	$base = product_code_exists_ref($code);
 
 #::logDebug("fly_page: code=$code base=$base page=" . substr($page, 0, 100));
 	return undef unless $base || $opt->{onfly};