add guard for self.weight.quant_state attribute

Author: winglian

bitsandbytes/nn/modules.py

@@ -515,7 +515,10 @@ def _save_to_state_dict(self, destination, prefix, keep_vars):
         save weight and bias,
         then fill state_dict with components of quant_state
         """
-        if getattr(self.weight.quant_state, "packing_format_for_cpu", False):
+        if (
+            getattr(self.weight, "quant_state", None) is not None
+            and getattr(self.weight.quant_state, "packing_format_for_cpu", False)
+        ):
             self.weight.data, self.weight.quant_state = _convert_weight_packed_for_cpu_inverse(
                 self.weight.data, self.weight.quant_state
             )