permission by_module - fix input check

Author: mickeyn

lib/MetaCPAN/Query/Permission.pm

@@ -39,9 +39,10 @@ sub by_author {
 sub by_modules {
     my ( $self, $modules ) = @_;
     $modules = [$modules] unless is_arrayref($modules);
-    return unless @{$modules};
 
-    my @modules = map +{ term => { module_name => $_ } }, @{$modules};
+    my @modules = map +{ term => { module_name => $_ } },
+        grep defined, @{$modules};
+    return unless @modules;
 
     my $body = {
         query => {