Describe the bug
I aim trying to deserialize a yaml open api file, but it's getting NullReferenceException

OpenApi File To Reproduce
https://api.codacy.com/api/api-docs/swagger.yaml

Expected behavior
The document shoud be serialized correctly

Screenshots/Code Snippets

Code to reproduce available here:
https://github.com/lucassklp/Rx.Http.CodeGen/tree/ce2a7b97ec91ba09e56f3c77d62e1730abe1463d

Methods i'm calling:

Stacktrace:

Additional context
Version: 2.0.0-preview2