WebProtege can't display certain classes (e.g. from the DPV ontology)

[csnyulas]

Describe the bug
Many classes in the OWL ontologies published as part of the W3C Data Privacy Vocabulary (DPV) cannot be displayed in WebProtege.

To Reproduce
Steps to reproduce the behavior:

1. Download an OWL ontology module from the DPV GitHub Repository, for example the core DPV module (of DPV version 2.0) https://github.com/w3c/dpv/blob/master/2.0/dpv/dpv-owl.rdf
2. Create a new Project in WebProtege by using the file downloaded in step 1, to initialize the project content
3. Navigate through the classes, some will throw an error. For example in the DPV ontology, click on the "Processing" class
4. See error
   

Expected behavior
To see the content of all the classes rendered properly

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: Windows
• Browser Chrome
• Version 129

Additional context
The problem may be related to the presence of some blank nodes, that are meant to encode source information. However, after removing all the blank nodes from the RDF file in a text editor, and updated the WebProtege project with the new file (through the Project --> Apply External Edits menu option), I still got some further errors (could be related to the existence of some erroneous information that was not deleted during the update, but this is just a wild guess),