GH-4622 SHACL preserve bnode (simple solution)

[hmottestad]

GitHub issue resolved: #4622

Briefly describe the changes proposed in this PR:

This is a simple solution that fixes the issue in a backwards compatible manner.

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PR Author Checklist (see the contributor guidelines for more details):

• my pull request is self-contained
• I've added tests for the changes I made
• I've applied code formatting (you can use mvn process-resources to format from the command line)
• I've squashed my commits where necessary
• every commit message starts with the issue number (GH-xxxx) followed by a meaningful description of the change