Error exporting cucumber Tests

Exporting cucumber Tests which currently have, or previously had, issue description fails unexpectedly, either via public API or the UI.

Steps to reproduce:

1. Create a Test.
2. In the Test Details, set the Test Type to Cucumber, and add a Cucumber definition.
3. Export the cucumber feature file.
   Actual result: The export is successful.
4. Add some description to the issue.
5. Export the cucumber feature file.
   Actual result: The export fails.
6. Edit the description and clear it entirely.
7. Export the cucumber feature file.
   Actual result: The export fails.