Index: image.module
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/image/image.module,v
retrieving revision 1.209.2.41
diff -u -p -u -r1.209.2.41 image.module
--- image.module	8 Aug 2007 16:21:35 -0000	1.209.2.41
+++ image.module	22 Aug 2007 16:59:16 -0000
@@ -302,7 +302,7 @@ function image_prepare(&$node, $field_na
   if ($file = file_check_upload($field_name)) {
     // Ensure the file is an image.
     $image_info = image_get_info($file->filepath);
-    if (!$image_info || !isset($image_info['extension'])) {
+    if (!$image_info || empty($image_info['extension'])) {
       form_set_error($field_name, t('Uploaded file is not a valid image. Only JPG, PNG and GIF files are allowed.'));
       return;
     }