Users able to create subtask with no parent via Jira mail handler

Summary

When user creates an Incoming Mail handler they are able to specify the issue type as sub-task. They are not given the option to set the parent on this sub-task.

Environment

Jira Core

Steps to Reproduce

1. Go to Administration > System
2. Choose Incoming Mail from left hand navigation
3. Choose Add incoming mail handler
4. Choose Create a new issue or add and issue to an existing issue
5. Choose project
6. Set issue type to Sub-task
7. Fill other fields as necessary (defaults should be fine)
8. Save handler and send email to project email address
9. Sub-task will be created with no parent

Expected Results

Sub-task should not be created without asking for parent

Actual Results

No error is throw but new subtask will be created in project specified in handler

Notes

This creates an orphaned subtask

Workaround

No