diff -u -r image-5.x-1.6/image.module image-5.x-1.6-patch-for-187054/image.module
--- image-5.x-1.6/image.module	2007-09-29 07:19:40.000000000 +0200
+++ image-5.x-1.6-patch-for-187054/image.module	2007-10-29 19:40:00.000000000 +0100
@@ -392,14 +392,17 @@
       // derivative size.
       $images = $node->images;
       unset($images[IMAGE_ORIGINAL]);
-      if (user_access('view original images') || in_array($filepath, $images)) {
+      if (user_access('view original images') ||
+        (is_array($images) && in_array($filepath, $images))) {
         return array(
           'Content-Type: '. mime_header_encode($file->filemime),
           'Content-Length: '. (int) $file->filesize,
         );
       }
     }
-    return -1;
+    if (is_array($node->images)) {
+      return -1;
+    }
   }
 }