Issue Summary

When creating a Sub-Task if their Wokflow has the Copy Value From Other Field Post-Function with the Copy from parent option set & it uses a Select List (cascading) Field there is an error if the Select List (cascading) Field chooses a value with no second value.

Steps to Reproduce

1. Create a Select List (cascading) Field with some options with no second level, like: 
2. 
3. Add a Copy Value From Other Field Post-Functionon to the Create Transition on a Workflow with Sub-Task Issue Types.
4. Select the created Select List (cascading) Field on the Source/Destination Fields & select the Copy from parent option: 
5. 
6. Addd the Post-Function & Publish the changes
7. Create a Sub-Task on an Issue with the Select List (cascading) Field with the option with no second level.

Expected Results

The Sub-Task is created

Actual Results

The Sub-Task is not created, the following error is displayed:

We can't create this issue for you right now, it could be due to unsupported content you've entered into one or more of the issue fields. If this situation persists, contact your administrator as they'll be able to access more specific information in the log file.

Workaround

The only workaround at this moment is to not use Select List (cascading) Fields with an option with no second level.