fix _tied_weights_keys format

modeling_moss_vl.py

@@ -2152,7 +2152,11 @@ class MossVLModel(MossVLPreTrainedModel):
     """
 )
 class MossVLForConditionalGeneration(MossVLPreTrainedModel, GenerationMixin):
-    _tied_weights_keys = ["lm_head.weight"]
+    # transformers 5.x expects a dict[target, source]; MossVL does not tie
+    # lm_head to the embeddings (config.tie_word_embeddings is False), so the
+    # mapping is empty. The legacy list format ["lm_head.weight"] breaks
+    # save_pretrained in transformers>=5.
+    _tied_weights_keys: dict[str, str] = {}
     config: MossVLConfig
     _checkpoint_conversion_mapping = {}
     accepts_loss_kwargs = False