Databind-error on simple jsonMapper.writeValueAsString()

[FrankMeissnerXledger]

Hello, while trying to get something useful from a weird response coming from an graphql-server, I met another obstacle.

Am I doing something wrong here? My intention was to write qrr, regardless of what fields it might or might not contain. The error the tests generates is the same as the one I got from my production-code (I used another QueryRootResponse, it was generated by graphql-maven-plugin).

The test was written in the graphql-java-client-runtime-project, since that's where com.graphql_java_generator.client.response.Error is located.

package com.graphql_java_generator.client.response;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.junit.jupiter.MockitoExtension;

import com.graphql_java_generator.domain.client.forum.QueryRootResponse;

import tools.jackson.databind.json.JsonMapper;

@ExtendWith(MockitoExtension.class)
public class ErrorTest {

	@Test
	void simple() throws Exception {
		final JsonMapper jsonMapper = new JsonMapper();
		final QueryRootResponse qrr = jsonMapper.readValue("""
			{
			  "errors": [
			    {
			      "message": "some error message"
			    }
			  ]
			}""", QueryRootResponse.class);
		
		jsonMapper.writeValueAsString(qrr);
	}
}

The test fails in the branch graphql-maven-plugin-project-4.0.2 with:

[ERROR] Errors: 
[ERROR]   ErrorTest.simple:26 » Databind Cannot invoke "java.util.Map.keySet()" because "this.extensionsAsMapOfJsonNode" is null
 at [No location information] (through reference chain: com.graphql_java_generator.domain.client.forum.QueryRootResponse["errors"]->java.util.ArrayList[0]->com.graphql_java_generator.client.response.Error["extensionsAsMapStringString"])

Greetings, Frank Meissner