Cleanup to make the catching of exceptions related to the Verifiable credential casting more clear.

[ouphi]

What this PR changes/adds

Cleanup to make the catching of exceptions related to the Verfiable credential casting more clear.

Checklist

• [ ] added appropriate tests?
• [ ] performed checkstyle check locally?
• [ ] added/updated copyright headers?
• [ ] documented public classes/methods?
• [ ] added/updated relevant documentation?
• [ ] added relevant details to the changelog? (skip with label no-changelog)
• [ ] formatted title correctly?