Status 415 - Unsupported Media Type

Hi everybody,
I am new with Katalon and I am facing a problem about a simple test of APIRest. I send a GET request, so body is not required. I set the url correctly and after sending the request I get response as in “Discussion Title” field. In body tab following message appears:

Malformed Media Type, expected a ‘/’ after the top type

I don’t understand how to solve the problem. Could you possibly giving me a help?
Many thanks in advance