editing someone else's question throws exception

observed in nightly qa oracle instance.

If more than one user has the maintain role in a site, they should be able to edit questions in each others' assessments as long as the questions are not drawn from question pools. Right now Samigo throws an exception if you try that. (see attached).

Steps to reproduce:

1. Log in as user #1. Go to a site in which #1 has the maintain role.
2. In the site, go to T&Q and create an assessment. Create a new question, any type, to go in the assessment. (Don't save it to a question pool.)
3. Go to the Site Info tool and grant user #2 the maintain role in the site. Log out.
4. Log in as user #2 and go to the site, then T&Q. You have the maintain role now, so you can view the new assessment.
5. Modify the question that user #1 created and click save.
6. Boom.

What should happen is that Samigo should check whether the question was imported from a question pool or created from scratch. If the question was created from scratch, user #2 should be able to edit it. (If the question came from a question pool, #2 should get a warning message - see linked issue).