Enter field is null for node when event type is error

[fjtirado]

Describe the bug

Issue apache/incubator-kie-issues#576 added a small change related with Node event types (a new state EVENT_TYPE_ERROR.
https://github.com/elguardian/kogito-apps/blob/d157e3a7595db61963c45d97173b22b02cbf335e/data-index/data-index-common/src/main/java/org/kie/kogito/index/event/mapper/ProcessInstanceNodeDataEventMerger.java#L72C13-L74C23
When the event is of this type, the enter field might be left empty, but according to graphql definition, enter is not nullable, causing this exception

Full Error as JSON
{
  "error": {
    "name": "CombinedError",
    "message": "[GraphQL] The field at path '/ProcessInstances[0]/nodes[7]/enter' was declared as a non null type, but the code involved in retrieving data has wrongly returned a null value.  The graphql specification requires that the parent field be set to null, or if that is non nullable that it bubble up null to its parent and so on. The non-nullable type is 'DateTime' within parent type 'NodeInstance'\n[GraphQL] The field at path '/ProcessInstances[0]/nodes[8]/enter' was declared as a non null type, but the code involved in retrieving data has wrongly returned a null value.  The graphql specification requires that the parent field be set to null, or if that is non nullable that it bubble up null to its parent and so on. The non-nullable type is 'DateTime' within parent type 'NodeInstance'",
    "graphQLErrors": [
      {
        "message": "The field at path '/ProcessInstances[0]/nodes[7]/enter' was declared as a non null type, but the code involved in retrieving data has wrongly returned a null value.  The graphql specification requires that the parent field be set to null, or if that is non nullable that it bubble up null to its parent and so on. The non-nullable type is 'DateTime' within parent type 'NodeInstance'",
        "path": [
          "ProcessInstances",
          0,
          "nodes",
          7,
          "enter"
        ],
        "extensions": {
          "classification": "NullValueInNonNullableField"
        }
      },
      {
        "message": "The field at path '/ProcessInstances[0]/nodes[8]/enter' was declared as a non null type, but the code involved in retrieving data has wrongly returned a null value.  The graphql specification requires that the parent field be set to null, or if that is non nullable that it bubble up null to its parent and so on. The non-nullable type is 'DateTime' within parent type 'NodeInstance'",
        "path": [
          "ProcessInstances",
          0,
          "nodes",
          8,
          "enter"
        ],
        "extensions": {
          "classification": "NullValueInNonNullableField"
        }
      }
    ],
    "response": {}
  },
  "request": {
    "method": "GET",
    "url": "/instances/b9af370f-b873-4191-a43a-2b50bfd9d0e3"
  },
  "response": {
    "statusCode": 500
  }
}

Expected behavior

Enter should be always filled

Actual behavior

Enter is null when even type is error

How to Reproduce?

No response

Output of uname -a or ver

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Output of java -version

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GraalVM version (if different from Java)

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Kogito version or git rev (or at least Quarkus version if you are using Kogito via Quarkus platform BOM)

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Build tool (ie. output of mvnw --version or gradlew --version)

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Additional information

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