Since MDL-73549 the My course page breaks when some course category is hidden.

Steps to reproduce:

1. Create a new course category and click the eye to hide it.
2. Log in as a normal user (user "t1" if you use MDK)
3. Go to "My courses"
   1. Expected: my courses page is displayed
   2. What happens: an exception

The errors are due to the method get_nearest_editable_subcategory. In one of the lines it get a category using:

$subcategory = static::get($subcategoryid);

The main problem with the get method is that by default it checks the user permission and raises an exception unless $alwaysreturnhidden param is true.