[Enhancement] Do not print config if it is empty (#1028)

mmengine/runner/runner.py

@@ -2290,7 +2290,9 @@ class Runner:
                          env_info + '\n'
                          '\nRuntime environment:' + runtime_env_info + '\n' +
                          dash_line + '\n')
-        self.logger.info(f'Config:\n{self.cfg.pretty_text}')
+
+        if self.cfg._cfg_dict:
+            self.logger.info(f'Config:\n{self.cfg.pretty_text}')
 
     def _maybe_compile(self, target: str) -> None:
         """Use `torch.compile` to optimize model/wrapped_model."""