--- imagecache_profiles.module
+++ (clipboard)
@@ -65,7 +65,9 @@
 
     if (isset($picture)) {
       $alt = t("@user's picture", array('@user' => $account->name ? $account->name : variable_get('anonymous', t('Anonymous'))));
-      $preset = is_numeric($size) ? imagecache_preset($size) : imagecache_preset_by_name($size);
+      if (isset($size)) {
+        $preset = is_numeric($size) ? imagecache_preset($size) : imagecache_preset_by_name($size);
+      }
       if (empty($preset)) {
         $variables['picture'] = $default; //theme('image', $picture, $alt, $alt, '', FALSE);
       }