What you would like to accomplish:

Vulnerability found for outdated libraries, however, the Vulnerable URLs is empty.

There isn't necessarily a URL that would exist for all outdated libraries. In order to make the user experience coherent and to avoid any confusion, the Vulnerable URL section in UI for this particular type of finding should be removed or should be populated with relevant a url.

How this might work:

Populate the Vulnerable URL section with relevant URL instead.