Serializing an OpenAPI document as V2 throws an error "Value cannot be null. (Parameter 'source')" when InlineLocalReferences = true e.g.,

OpenApiWriterBase writer = new OpenApiYamlWriter(sr,
                        new OpenApiWriterSettings { InlineLocalReferences = true});

The error gets thrown when serializing the OpenAPI document as V2, i.e., OpenApiDocument.SerializeAsV2(writer)

This affects both OpenApiJsonWriter and OpenApiYamlWriter classes.
This affects the latest version of Microsoft.OpenAPI.Readers v1.3.1