Guest role cannot access folder content....

One of my customers reported that one of her courses that allows guest access, with an enrollment key, was erroring when trying to access a folder in the course.

This is the error:

Fatal error: Call to a member function get_url() on a non-object in C:\wamp\www\training\mod\folder\renderer.php on line 70 Call Stack: 0.0009 714128 1. {main}() C:\wamp\www\training\mod\folder\view.php:0 0.7120 49524856 2. mod_folder_renderer->folder_tree() C:\wamp\www\training\mod\folder\view.php:76 0.7146 49549032 3. plugin_renderer_base->render() C:\wamp\www\training\mod\folder\renderer.php:38 0.7147 49549120 4. mod_folder_renderer->render_folder_tree() C:\wamp\www\training\lib\outputrenderers.php:215 0.7147 49550000 5. mod_folder_renderer->htmllize_tree() C:\wamp\www\training\mod\folder\renderer.php:45 0.7154 49551072 6. mod_folder_renderer->htmllize_tree() C:\wamp\www\training\mod\folder\renderer.php:65

After spending about an hr messing with the role permissions and trying a backup and restore workaround, I punted and went to try to find any information around this error.  I tried a couple combinations of search strings like "moodle access folder problem guest role" or "guest role cannot access folder in course" and probably a couple other combinations, but only got moodle doc pages in my result set.

Eventually, I tried something like "folder/view error guest access" and found a tracker issue!  That was a good sign.  This is the link to the tracker issue. I search for the tracker issue # in the latest release of moodle 2.3.2 (which I do not yet have installed).  But sadly did not find it in the 2.3.2 release notes.

BUT, I did find a comment in the tracker issue where someone posted a workaround until the bug fix was released.  This is the update to a core file that solved the problem.  Thanks so much to Sebastian Michel

While waiting for a definitive patch from the core developers, here is a quick fix (at your own risks!). In lib/filebrowser/file_info_context_module.php in get_file_info function
replace:
if (!is_viewing($this->context) and !is_enrolled($this->context)) {
with:
if (!is_viewing($this->context) and !is_enrolled($this->context) and !is_guest($this->context)) {