[BUG] OpenAPI failed to initialized variables while generating the code

Bug Report Checklist

Here is my spec file

    Portfolios:
      allOf:
        - $ref: '#/components/schemas/DlCollection'
        - type: object
          properties:
            items:
              type: array
              items:
                $ref: '#/components/schemas/Portfolio'

Open API 6.6.0 version generating code like below

@Generated(value = "org.openapitools.codegen.languages.SpringCodegen")
public class Portfolios extends DlCollection implements Serializable {

  private static final long serialVersionUID = 1L;

  @JsonProperty("items")
  @Valid
  private List<Portfolio> items = null;

My expectation is

  @JsonProperty("items")
  @Valid
  private List<Portfolio> items = new ArrayList<>();

Is there any fix or workaround for this?

Start by reproducing Java SpringCodegen output with the supplied OpenAPI schema on version 6.6.0, then trace the generator path that initializes the Portfolios.items field. Compare the generated null initialization with the expected ArrayList initialization; done means the generated field uses the expected default without regressing related schemas.