[Java/Jaxrs/Resteasy] NPE thrown when response is defined with $ref without content

[tnmtechnologies]

Description

We wanted to fix #8859 in OpenAPITools/openapi-generator thanks to this PR OpenAPITools/openapi-generator/pull/1416

Then we faced this issue OpenAPITools/openapi-generator/issues/1420.
This issue seems to come from swagger parser.

Please what is your point of view?

Swagger-codegen version

OpenAPITools/openapi-generator 3.3.3-SNAPSHOT

Swagger declaration file content or url

Command line used for generation

Steps to reproduce

Related issues/PRs

#8859
OpenAPITools/openapi-generator/pull/1416
OpenAPITools/openapi-generator/issues/1420

Suggest a fix/enhancement

[tnmtechnologies]

This issue can be deleted because it was not created in the right repository.