Resolve "Vulnerability report shows empty state if there are no pipelines"

What does this MR do and why?

It makes sure that the project-level vulnerability report does not show the empty state when no pipeline has run. This is to make sure that manually added vulnerabilities are showing up in those cases.

Screenshots or screen recordings

before	after

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #339730 (closed)