polish code

Author: sycai

bigframes/core/compile/sqlglot/expressions/ai_ops.py

@@ -104,7 +104,7 @@ def _construct_named_args(op: ops.NaryOp) -> list[sge.Kwarg]:
 
     op_args = asdict(op)
 
-    connection_id = op_args.get("connection_id")
+    connection_id = op_args.get("connection_id", None)
     if connection_id is not None:
         args.append(
             sge.Kwarg(