small performance improvement

I have enabled the E_NOTICE level, and I always get a warning
notice: Undefined index: #node in D:\develop\xampp\htdocs\drupal\modules\advanced_forum\advanced_forum.module on line 318.

function advanced_forum_form_alter(&$form, &$form_state, $form_id) {
  if (advanced_forum_type_is_in_forum($form['#node']->type)) {
  //  [...]

advanced_forum_type_is_in_forum allways makes a call to advanced_forum_get_forum_types
maybe some of these calls can be avoid just checking #node

function advanced_forum_form_alter(&$form, &$form_state, $form_id) {
  if (isset($form['#node']) && advanced_forum_type_is_in_forum($form['#node']->type)) {
  //  [...]

Hope it helps.