* Removed a warning

functions/prefs.php

@@ -103,7 +103,7 @@
       global $prefs_cache;
       
       cachePrefValues($data_dir, $username);
-      if ($prefs_cache[$string] == $set_to)
+      if (isset($prefs_cache[$string]) && $prefs_cache[$string] == $set_to)
          return;
       if ($set_to == '') {
          removePref($data_dir, $username, $string);