I am working with quiz and adding questions (multiple choice) to a quiz.
After a while, I decided to delete revisions in the quiz admin page to leave only the current revision.
Now visiting the quiz 'view' page shows no errors and the correct number of questions in the quiz.
Clicking on the 'Take' tab though results in the mentioned error:
Notice: Trying to get property of non-object in quiz_take_quiz() (line 1870 of /sites/all/modules/quiz/quiz.module)

In addition to this error, there's a slew of other errors:

Notice: Trying to get property of non-object in quiz_take_quiz() (line 1870 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in _quiz_delete_old_in_progress() (line 3193 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in _quiz_delete_old_in_progress() (line 3193 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_take_quiz() (line 1876 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_take_quiz() (line 1876 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_take_quiz() (line 1879 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_start_check() (line 2683 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_start_check() (line 2688 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_start_check() (line 2701 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_start_check() (line 2727 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_build_question_list() (line 2898 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_build_question_list() (line 2909 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_build_question_list() (line 2915 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_build_question_list() (line 2925 of sites/all/modules/quiz/quiz.module).
No questions were found. Please assign questions before trying to take this  Quiz.
Notice: Trying to get property of non-object in quiz_take_quiz() (line 1902 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_take_quiz() (line 2015 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_take_quiz() (line 2130 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_take_quiz() (line 2137 of sites/all/modules/quiz/quiz.module).
Notice: Undefined index: quiz_ in quiz_take_quiz() (line 2137 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in _quiz_get_answers() (line 3706 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_take_quiz() (line 2138 of sites/all/modules/quiz/quiz.module).
Notice: Undefined index: quiz_ in quiz_take_quiz() (line 2138 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_calculate_score() (line 2810 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_end_scoring() (line 2360 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_end_scoring() (line 2360 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_take_quiz() (line 2139 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in _quiz_get_summary_text() (line 3333 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in _quiz_get_summary_text() (line 3333 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in _quiz_get_summary_text() (line 3339 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in _quiz_get_summary_text() (line 3367 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in theme_quiz_take_summary() (line 516 of sites/all/modules/quiz/quiz.pages.inc).
Notice: Trying to get property of non-object in theme_quiz_take_summary() (line 535 of sites/all/modules/quiz/quiz.pages.inc).
Notice: Trying to get property of non-object in quiz_take_quiz() (line 2149 of sites/all/modules/quiz/quiz.module).
Notice: Undefined index: quiz_ in quiz_take_quiz() (line 2149 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in _quiz_maintain_results() (line 4053 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in _quiz_maintain_results() (line 4060 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_take_quiz() (line 2153 of sites/all/modules/quiz/quiz.module).
Notice: Undefined index: quiz_ in quiz_take_quiz() (line 2153 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_take_quiz() (line 2154 of sites/all/modules/quiz/quiz.module).
Notice: Trying to get property of non-object in quiz_quiz_finished() (line 2420 of sites/all/modules/quiz/quiz.module).

Please note the error included above:

No questions were found. Please assign questions before trying to take this  Quiz.

Additionally, at bottom of these errors, I have this message:
You are marked as an administrator or owner for this quiz. While you can take this quiz, the open/close times prohibit other users from taking this quiz.
With no questions under it. This therefore breaks quiz as theres nothing to do after this.
I have not set any time limits to this quiz (0) in quiz configurations.

Files: 
CommentFileSizeAuthor
quiz1.jpg70.02 KBkenyan

Comments

I'm wondering if this has anything to do with quiz trying to locate results etc of previous takes as I was testing but not finding revisions as I've deleted them.
Database updates and cache clears make no difference.
I may have to uninstall and start over but will wait on responses first.