Fatal error: Call to a member function on a non-object in questiontype.php during quiz attempts

Fatal error: Call to a member function on a non-object in /home/myservername/public_html/moodle/question/type/random/questiontype.php on line 242 occurs when a quiz including random questions is in Adaptive mode and then ONLY when at least one question has been submitted individually before the Submit All and Finish Button has been pressed.

The quiz works fine as long as none of the questions are submitted individually. The error always occurs upon attempting to go to the next question after any of them has been submitted indivdiually. This prevents using the quiz module in adaptive mode as a review for a test!

Settings that cause problem...
Questions per page: 1
Shuffle questions: Yes
Shuffle within quesitons: Yes
Attempts allowed: Unlimited attempts
Each attempt builds on the last: No
Grading method: Highest grade
Adaptive mode: yes
Apply penalties: yes
Decimal digits: 2
Students may view: Immediately after attempt: Responses, Scores, Feedback General Feedback
Time delay: None
Show quiz in secure window: No
No Groups