Null APIResponse with v1.3.5

[anuragpro]

https://stackoverflow.com/questions/61529174/null-apiresponse-when-migrating-from-springfox-to-springdoc/61535934#61535934

v1.3.4 seems to be working.

[bnasslahsen]

@anuragpro,

This is duplicate of #630.
You can test with the fix already deployed on master and which will be released in v1.3.8.