Index: /branches/release-40/lib/MT/Asset/Image.pm
===================================================================
--- /branches/release-40/lib/MT/Asset/Image.pm (revision 1927)
+++ /branches/release-40/lib/MT/Asset/Image.pm (revision 2561)
@@ -295,5 +295,5 @@
         }
 
-        if ( $param->{popup} ) {
+        if ( $param->{popup} && $param->{popup_asset_id} ) {
             my $popup = MT::Asset->load( $param->{popup_asset_id} )
               || return $asset->error(