Cached pages give "call to undefined function" error

I'm using Visibility API with caching enabled (normal caching, not aggressive). I found that whenever you log out and visit a cached page, you get a white screen of death with this error message:

Fatal error: Call to undefined function drupal_add_js() in /web/sites/all/modules/visibility_api/visibility_api.module on line 13

The problem is that in Drupal 5, drupal_add_js() should not be called in hook_init() since this function is not available on cached pages. See http://api.drupal.org/api/function/hook_init/5.

Here is a patch that fixes this by moving the code to hook_menu(), as suggested on that page. You may want to try a different solution instead, but this fixes the bug.

Thanks!