skip dock step when Dockerfile not present

Author: LiNk-NY

.github/workflows/pr_check.yml

@@ -27,6 +27,10 @@ jobs:
         run: |
           MATRIX="{\"include\":[{\"bioc_version\":\"$GITHUB_REF_NAME\"}]}"
           echo "matrix=$MATRIX" >> $GITHUB_OUTPUT
+      - name: Check for Dockerfile
+        id: dockfile_check
+        run: |
+          echo "exists=$( [ -f ./inst/docker/pkg/Dockerfile ] && echo true || echo false )" >> $GITHUB_OUTPUT
 
   check:
     needs: set-matrix
@@ -117,7 +121,7 @@ jobs:
           path: docs
 
   dock:
-    if: ${{ github.ref == 'refs/heads/devel' }}
+    if: ${{ github.ref == 'refs/heads/devel' && steps.dockerfile_check.outputs.exists == 'true' }}
     runs-on: ubuntu-24.04
     needs: check
     steps: