I am seeing the following fatal error when trying to load Site Administration -> Grades -> Outcomes:

Fatal error: Call to a member function load_items() on a non-object in /mnt/code/www/moodle_prod/lib/grade/grade_outcome.php on line 212

After some investigation I have discovered that there is some outcomes associated with a scale id that was deleted.

The scale appears to have at first been a standard scale (course id 0) and attached to multiple site wide out comes. Then the scale was moved to a course by being edited in the course level and unchecking the standard checkbox. That course was eventually deleted which triggered that scale to be deleted, leaving behind outcomes that were still associated with it.

Steps to replicate:

Create a Scale at the site level
Create an outcome at the site level, attaching it to the scale you just created
Create a course and go into the course and view scales
Edit the scale you just created and uncheck the Standard Scale box (makes it a course scale)
Delete the course you just created
Try to load Site Administration -> Grades -> Outcomes