remove lm head if unused (#1324)

llms/mlx_lm/models/llama.py

@@ -196,9 +196,12 @@ class Model(nn.Module):
 
     def sanitize(self, weights):
         # Remove unused precomputed rotary freqs
-        return {
+        weights = {
             k: v for k, v in weights.items() if "self_attn.rotary_emb.inv_freq" not in k
         }
+        if self.args.tie_word_embeddings:
+            weights.pop("lm_head.weight", None)
+        return weights
 
     @property
     def layers(self):