NIFI-12918 Fix Stateless NullPointerException on versioned sub-process groups

[slambrose]

Summary

NIFI-12918

This is the PR for the 2.0 (main) branch: #8536

Tracking

Please complete the following tracking steps prior to pull request creation.

Issue Tracking

• Apache NiFi Jira issue created

Pull Request Tracking

• Pull Request title starts with Apache NiFi Jira issue number, such as NIFI-00000
• Pull Request commit message starts with Apache NiFi Jira issue number, as such NIFI-00000

Pull Request Formatting

• [-] Pull Request based on current revision of the main branch | We need this to be based on support/nifi1.x
• Pull Request refers to a feature branch with one commit containing changes

Verification

Please indicate the verification steps performed prior to pull request creation.

Build

• Build completed using mvn clean install -P contrib-check
• [-] JDK 21 | we built this to support nifi version 1.x which is on JDK 11

Licensing

• New dependencies are compatible with the Apache License 2.0 according to the License Policy - no new dependencies
• New dependencies are documented in applicable LICENSE and NOTICE files

Documentation

• Documentation formatting appears as expected in rendered files

[exceptionfactory]

Based on the system test failures in the associated pull request for the main branch, this current pull request should not go forward until those failures are resolved.

[exceptionfactory]

This pull request also fails on the same integration tests as PR #8536 for the main branch.

[ERROR]   RegistryClientIT.testChangeConnectionDestinationRemoveOldAndMoveGroup:166 » NiFiClient Error starting version control: An unexpected error has occurred. Please check the logs for additional details.
[ERROR]   RegistryClientIT.testChangeVersionOnParentThatCascadesToChild:95 » NiFiClient Error starting version control: An unexpected error has occurred. Please check the logs for additional details.
[ERROR]   RegistryClientIT.testChangeVersionWithPortMoveBetweenGroups:265 » NiFiClient Error creating process group: An unexpected error has occurred. Please check the logs for additional details.
[ERROR]   RegistryClientIT.testControllerServiceUpdateWhileRunning:221 » NiFiClient Error starting version control: An unexpected error has occurred. Please check the logs for additional details.
[ERROR]   RegistryClientIT.testCopyPasteProcessGroupDoesNotDuplicateVersionedComponentId:409 » NiFiClient Error starting version control: An unexpected error has occurred. Please check the logs for additional details.
[ERROR]   RegistryClientIT.testCopyPasteProcessGroupUnderVersionControlMaintainsVersionedComponentId:459 » NiFiClient Error starting version control: An unexpected error has occurred. Please check the logs for additional details.
[ERROR]   RegistryClientIT.testRollbackOnFailure:312 » NiFiClient Error creating process group: An unexpected error has occurred. Please check the logs for additional details.
[ERROR]   RegistryClientIT.testStartVersionControlThenImport:335 » NiFiClient Error starting version control: An unexpected error has occurred. Please check the logs for additional details.
[ERROR]   RegistryClientIT.testStartVersionControlThenModifyAndRevert:372 » NiFiClient Error starting version control: An unexpected error has occurred. Please check the logs for additional details.

This can be tested locally using the following build command, after building the project:

./mvnw verify -P integration-tests -pl :nifi-system-test-suite -Dtest=RegistryClientIT

[exceptionfactory]

I'm closing this pull request for now so that we can focus on making the correct changes on the main branches. The automated builds did not trigger the system tests, but running them locally confirms that the same issues exist on the support branch right now. We can continue the review process on PR #8536 and the associated Jira issue, then either this PR can be reopened, or a new PR can be created to implement a solution.