Add condition to `benchmark` job in `push-important-models.yml` (#31259)

fix
Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>

.github/workflows/push-important-models.yml

@@ -136,5 +136,7 @@ jobs:
 
   benchmark:
     name: Benchmark workflow
+    needs: get_modified_models
+    if: ${{ needs.get_modified_models.outputs.matrix != '[]' && needs.get_modified_models.outputs.matrix != '' && fromJson(needs.get_modified_models.outputs.matrix)[0] != null }}
     uses: ./.github/workflows/benchmark.yml
     secrets: inherit