Error after editing the poll with the same choises.

There is error 500 after editing the poll with same choises.

How to reproduce:
1. Login and open forum. Create a new poll.
2. Insert 2 equal choises for the poll.
3. Save topic.
4. Open this topic for editing, but do nothing.
5. Save topic. You can see only choise for voting (see att.).
6. Open the topic for editing one more time. There is only line in Options list field. But it's necessary to have 2 or more lines there.
7. Add one more line (copy/past) in Options list field.
8. Try to save it.

AR: error 500.
EP: topic saved successfully.