Associating test cases to test plan via API not returning response

Description
When associating a test with a test plan via API we get no response even tho it is successful. 
Even if it is an invalid issue type.

Pre-conditions
- Have a test, a test plan, and a different issue created;

How to reproduce

1. In the endpoint add the Test Plan Key
2. Add in the body the Test Key and other issue type key

Actual result/Attachments

We get a "[]" response

Expected result
we should get a response:
["Test or Test Set with key CALC-29 not found or is not Type Test or Test Set"]

Version

• 7.4.1-J9