kernelCTF: GHA: fix vuln-verify 2

.github/workflows/kernelctf-vuln-verify.yaml

@@ -18,6 +18,7 @@ jobs:
     env:
       GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       PR_REF: ${{ contains(github.event_name, 'workflow_') && format('refs/pull/{0}/merge', inputs.prNumber) || github.event.pull_request.head.sha }}
+      PR_NUM: ${{ contains(github.event_name, 'workflow_') && inputs.prNumber || github.event.pull_request.number }}
     steps:
       - name: Authenticate to Google Cloud
         uses: google-github-actions/auth@v3
@@ -56,7 +57,7 @@ jobs:
       - name: Determine submission folder
         id: determine_folder
         run: |
-          FILES=$(gh pr view ${{ steps.pr_metadata.outputs.pr_number }} --json files --jq '.files[] | .path')
+          FILES=$(gh pr view $PR_NUM --json files --jq '.files[] | .path')
           echo "Files in PR:"
           echo "$FILES"