Fix bug when layer has 'branch' in name (#3148)

Fix bug when layer has 'branch' in name

Signed-off-by: Michael Tuttle <quic_mtuttle@quicinc.com>

TrainingExtensions/onnx/src/python/aimet_onnx/quantsim_config/quantsim_config.py

@@ -152,10 +152,10 @@ def _map_quantizers_to_ops(self) -> Dict[str, OpToQuantizers]:
         and output quantizers of an op
         """
         op_to_quantizers = {}
-        for name, op in self._conn_graph.get_all_ops().items():
-            if 'branch' in name:
-                continue
+        for _, op in self._conn_graph.get_all_ops().items():
             node = op.get_module()
+            if node is None:
+                continue
             op_to_quantizers[node.name] = OpToQuantizers()
             for input_product in node.input:
                 self._populate_input_and_param_quantizer(op_to_quantizers[node.name], input_product)