fix(mge/traced_module): fix bn opdef loader

GitOrigin-RevId: d73f953ef6

imperative/python/megengine/traced_module/compat.py

@@ -130,7 +130,8 @@ def convbn2d_module_loader(expr):
 @register_opdef_loader(BatchNorm)
 def bn_opdef_loader(expr):
     # mge 1.6
-    if not hasattr(expr, "version"):
+    if not hasattr(expr, "version") and len(expr.outputs) != 6:
+        assert len(expr.outputs) == 5
         output = expr.outputs[-1]
         oup = TensorNode(expr, shape=(0,), dtype=None, qparams=output._qparams,)
         expr.outputs.insert(4, oup)