enhance rewrite state_dict missing _metadata (#14348)

src/transformers/modeling_utils.py

@@ -1050,7 +1050,8 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin, GenerationMixin, PushToHubMix
         # Handle the case where some state_dict keys shouldn't be saved
         if self._keys_to_ignore_on_save is not None:
             for ignore_key in self._keys_to_ignore_on_save:
-                del state_dict[ignore_key]
+                if ignore_key in state_dict.keys():
+                    del state_dict[ignore_key]
 
         # If we save using the predefined names, we can load using `from_pretrained`
         output_model_file = os.path.join(save_directory, WEIGHTS_NAME)