User not informed that they cannot create sub-tasks under a sub-task issue type

[Don Brown]

Repro Steps

View a sub-task
Open Taskmaster Plugin
Add valid sub-tasks to create, then click "Submit"

Unexpected Behaviour

User not informed that they cannot create sub-tasks under a sub-task issue type
Confirmation message of successful creation of sub-tasks is returned to user, which is confusing since sub-tasks were actually not created.