Vat findings retrieval update

This MR fixes a bug in the findings retrieval which caused some findings to not be associated with a container

Tested with this branch: https://repo1.dso.mil/dsop/opensource/pipeline-test-project/gradle-jdk11/-/pipelines/364442 Confirmed that master branch of pipeline has unknown parent image findings: https://repo1.dso.mil/dsop/opensource/pipeline-test-project/gradle-jdk11/-/pipelines/364459

e.g.

{
  "opensource/gradle/gradle-jdk11": [...
  ],
  "redhat/ubi/ubi8": [...
  ],
  "", [...
  ]
}