NullPointerException when generating Bungie.net OpenAPI spec

Description

When trying to generate clients for the Bungie.net OpenAPI spec, I get a NullPointerException:

Exception in thread "main" java.lang.NullPointerException
	at org.openapitools.codegen.DefaultGenerator.processOperation(DefaultGenerator.java:939)
	at org.openapitools.codegen.DefaultGenerator.processPaths(DefaultGenerator.java:910)
	at org.openapitools.codegen.DefaultGenerator.generateApis(DefaultGenerator.java:488)
	at org.openapitools.codegen.DefaultGenerator.generate(DefaultGenerator.java:868)
	at org.openapitools.codegen.cmd.Generate.run(Generate.java:349)
	at org.openapitools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:62)

openapi-generator version

3.3.4-SNAPSHOT (master @ c656194f22f9624ee861abe57964758ae7e7bd39)

OpenAPI declaration file content or url

https://raw.githubusercontent.com/Bungie-net/api/master/openapi.json

Command line used for generation

java -jar openapi-generator-cli.jar generate \
      --generator-name php \
      --config         /local/openapi-config.php.json \
      --input-spec     https://raw.githubusercontent.com/Bungie-net/api/master/openapi.json \
      --output         /local/bungie-sdk-php \
      -DapiTests=false \
      -DmodelTests=false \
      --verbose

openapi-config.php.json:

{
  "packageName": "bungie-sdk-php",
  "composerVendorName": "yogarine",
  "composerProjectName": "bungie-sdk-php",
  "artifactVersion": "2.3.2",
  "invokerPackage" : "Bungie",
  "modelPackage": "Model",
  "apiPackage": "API",
  "variableNamingConvention": "camelCase",
  "srcBasePath": "src",
  "gitUserId": "Yogarine",
  "gitRepoId": "bungie-sdk-php",
  "validateSpec": false
}

Steps to reproduce

Build with the above command.

Reproduce the PHP generation command with the Bungie.net openapi.json URL, then inspect DefaultGenerator.java around processOperation (line 939) and processPaths (line 910). Done means the same command completes without the reported NullPointerException and generates the client output.