Try fixing empty base/head ref

action.yaml

@@ -10,7 +10,7 @@ runs:
       id: run-pear-reviewer
       uses: docker://ghcr.io/sapcc/pear-reviewer:edge
       with:
-        args: helm-chart
+        args: helm-chart --base ${{ github.event.pull_request.base.ref }} --head ${{ github.event.pull_request.head.ref }}
 
     - name: Find Comment
       uses: peter-evans/find-comment@v3