WIP: improve error message when mermaid exception is raised
What does this MR do?
Fix the flash exception showed when there is a syntax error that prevents mermaid diagram to show up.
Does this MR meet the acceptance criteria?
- Changelog entry
- Documentation created/updated or follow-up review issue created
- Code review guidelines
- Merge request performance guidelines
- Style guides
- Database guides
- Separation of EE specific content