fix(vd): fix object ref validation

[eofff]

Description

Return a named error when VirtualImage not found.

Why do we need it, and what problem does it solve?

What is the expected result?

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.

Changelog entries

section: vd
type: fix
summary: "return a named error when VirtualImage is not found to avoid throw handler error"
impact_level: low