Stash \undef to skip serialisation of body

The JSON serialiser (probably quite common) barfs if you try to serialise undef. This is probably good behaviour, because it means you've forgotten to stash the object you want serialising.

To explicitly skip serialisation, therefore, this patch allows you to pass a ref to undef.

lib/Catalyst/Action/Serialize.pm

@@ -34,6 +34,7 @@ sub execute {
                 $controller->{'stash_key'}
            ) || 'rest';
     return 1 if $c->response->status =~ /^(?:3\d\d)$/ && ! defined $c->stash->{$stash_key};
+    return 1 if ref $c->stash->{$stash_key} eq 'SCALAR' and not defined ${ $c->stash->{$stash_key} };
 
     my ( $sclass, $sarg, $content_type ) =
       $self->_load_content_plugins( "Catalyst::Action::Serialize",