core[patch]: consolidate conditional in BaseTool (#16530)

- **Description:** Refactor contradictory conditional to single line
  - **Issue:** #16528

libs/core/langchain_core/tools.py

@@ -111,8 +111,7 @@ class BaseTool(RunnableSerializable[Union[str, Dict], Any]):
 
         args_schema_type = cls.__annotations__.get("args_schema", None)
 
-        if args_schema_type is not None:
-            if args_schema_type is None or args_schema_type == BaseModel:
+        if args_schema_type is not None and args_schema_type == BaseModel:
             # Throw errors for common mis-annotations.
             # TODO: Use get_args / get_origin and fully
             # specify valid annotations.