Signatures tab with all node types

The problem is here:

if (arg(0) == 'node' && is_numeric(arg(1))) { 
      // put signatures in a tab on the node
      $items[] = array(
        'path' => 'node/'. arg(1) .'/signatures',
        'callback' => 'signit_view_signit_comments',
        'title' => t('Signatures'),
        'callback arguments' => arg(1),
        'access' => user_access('view signit comments'),
        'weight' => 1,
        'type' => MENU_LOCAL_TASK
      );

The signature tab is being applied to all nodes. I changed to the below code (sorry, I don't know how to make proper patches) and now I only get the "Signatures" tab on singit-enabled nodes.

if (arg(0) == 'node' && is_numeric(arg(1)) && variable_get("signit_status_$node->type", true)) { 
      // put signatures in a tab on the node

Scratch that last 'solution', as it didn't actually work. Here's an imitation of how signUP module handles it's tab-adding that actually does work. Just replace the IF code shown above as follows:

    if (arg(0) == 'node' && is_numeric(arg(1))) { 
      // put signatures in a tab on the node
      $node = node_load(arg(1));
      if (!empty($node->signit)) {
        $items[] = array(
          'path' => 'node/'. arg(1) .'/signatures',
          'callback' => 'signit_view_signit_comments',
          'title' => t('Signatures'),
          'callback arguments' => arg(1),
          'access' => user_access('view signit comments'),
          'weight' => 1,
          'type' => MENU_LOCAL_TASK
        );
      }