fix self query constructor (#12349)

libs/langchain/langchain/retrievers/self_query/base.py

@@ -203,11 +203,17 @@ class SelfQueryRetriever(BaseRetriever, BaseModel):
             structured_query_translator = _get_builtin_translator(vectorstore)
         chain_kwargs = chain_kwargs or {}
 
-        if "allowed_comparators" not in chain_kwargs:
+        if (
+            "allowed_comparators" not in chain_kwargs
+            and structured_query_translator.allowed_comparators is not None
+        ):
             chain_kwargs[
                 "allowed_comparators"
             ] = structured_query_translator.allowed_comparators
-        if "allowed_operators" not in chain_kwargs:
+        if (
+            "allowed_operators" not in chain_kwargs
+            and structured_query_translator.allowed_operators is not None
+        ):
             chain_kwargs[
                 "allowed_operators"
             ] = structured_query_translator.allowed_operators