Fatal Error: Class name must be a valid object or a string in ../quiz/question_types/quiz_question/quiz_question.module on line 646

Fatal Error: Class name must be a valid object or a string in ../quiz/question_types/quiz_question/quiz_question.module on line 646

Hi

I'm getting this error when trying to view previously passed quizzes as in node/%/quiz-results/%/view

The call stack is:
Call Stack
# Time Memory Function Location
1 0.0001 633832 {main}( ) ../index.php:0
2 1.2230 12049888 menu_execute_active_handler( ) ../index.php:21
3 1.2231 12050840 call_user_func_array ( ) ../menu.inc:527
4 1.2231 12051176 quiz_user_results( ) ../menu.inc:527
5 1.2782 14183728 quiz_calculate_score( ) ../quiz.pages.inc:25
6 1.3035 14210184 _quiz_question_response_get_instance( ) ../quiz.module:2438

Going to a page the following message is then displayed:

"The module for the questiontype is not enabled" which appear to be generate in quiz_question_module_for_type() in quiz.module line 2470.

This may be a seperate problem but I'm fairly certain that both are being caused by a question related to the quiz having been deleted. Just before the line where the error is reported there is:

  if (!isset($question)) {
    $question = node_load($nid, $vid);
  }

  $constructor = $info[$question->type]['response provider'];
  $to_return = new $constructor($result_id, $question, $answer);

I suspect that either there should be a check if $question has been loaded or the code should not have got this far with a question that is no longer available.

I will investigate further and try to find the root cause and create a patch.