Fix "Failed opening default pref" bug, closes #680331, thanks David Walser

functions/file_prefs.php

@@ -179,7 +179,7 @@ function checkForPrefs($data_dir, $username, $filename = '') {
     /* Then, check if the file exists. */
     if (!@file_exists($filename) ) {
         /* First, check the $data_dir for the default preference file. */
-        $default_pref = $data_dir . 'default_pref';
+        $default_pref = $data_dir . '/default_pref';
 
         /* If it is not there, check the internal data directory. */
         if (!@file_exists($default_pref)) {