Update Dockerfile

Dockerfile

@@ -26,7 +26,5 @@ RUN mkdir logs && chmod 777 logs
 RUN pipx install poetry
 
 RUN make install_frontend && make build_frontend && make install_backend
-
-# Update the config.yaml file, build and install the langflow package
-
+RUN if [ ! -d src/backend/base/langflow/frontend ] || [ ! "$(ls -A src/backend/base/langflow/frontend)" ]; then echo 'Folder src/backend/base/langflow/frontend does not exist or is empty'; exit 1; fi
 CMD ["make", "start", "host=0.0.0.0", "port=7860", "log_level=debug"]