Mentioning the Test Plan field as a mandatory in create/edit existing issue screen does not work while creating the Test Execution.

Description: Mentioning the Test Plan field as a mandatory in create issue screen does not work while creating the Test Execution. 

How to reproduce

1. Set the Test Plan as mandatory field.
2. Create Test execution. 
3. Leave the Test Plan field as blank. 
4. Create the Test execution. 
   

Actual result/Attachments

Test Execution is created without the error

Expected result

Test execution should not be created without filling the Test Plan after setting the filed as mandatory.