Update packages/bigframes/bigframes/core/compile/sqlglot/sql/base.py

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: shuoweil

packages/bigframes/bigframes/core/compile/sqlglot/sql/base.py

@@ -69,7 +69,7 @@ def literal(value: typing.Any, dtype: dtypes.Dtype | None = None) -> sge.Express
         return sge.Null()
 
     if value is None:
-        if sqlglot_type.upper() == "NULL":
+        if str(sqlglot_type).upper() == "NULL":
             return sge.Null()
         return cast(sge.Null(), sqlglot_type)
     if dtypes.is_struct_like(dtype):