Quiz manual grading: page size preference can get stuck at 0

Initial setup Create a course. Create a teacher and a student account. Create a Quiz activity. Create an Essay question and add it to the created Quiz activity. Testing Log in as a student. Attempt the Quiz and submit the answer. Log in as a teacher. Go to the Manual grading report of the Quiz. Click on the "grade" link in the report table. Set the Questions per page value to 0 and press "Change options". Verify that you will see an error message:  You must enter a number not starting with a 0 here . Set the Questions per page value to 1 and Press "Change options". Verify that you will not see an error message:  You must enter a number not starting with a 0 here . Verify that in the address bar of the browser, you will see something like:  &pagesize=1 . Change the  &pagesize=1 to  &pagesize=0 and press Enter. Verify that you will see an exception error:  Invalid page size . Remove the  &pagesize=0 and press Enter. Verify that the page will load successfully. Verify that the Questions per page value is 1 .  Also try eintering other non-standard values, like 'frog' or -7.