🦄 refactor(dataset svc): delete check none (#4101)

Co-authored-by: baxiang <baxiang@lixiang.com>

api/services/dataset_service.py

@@ -131,13 +131,9 @@ class DatasetService:
 
     @staticmethod
     def get_dataset(dataset_id):
-        dataset = Dataset.query.filter_by(
+        return Dataset.query.filter_by(
             id=dataset_id
         ).first()
-        if dataset is None:
-            return None
-        else:
-            return dataset
 
     @staticmethod
     def check_dataset_model_setting(dataset):