修复BUG，解决分页查询知识库列表时无法根据标签id查询的问题

api/services/dataset_service.py

@@ -135,7 +135,8 @@ class DatasetService:
                                                                               category_ids)
             if target_ids_by_category_ids:
                 query = query.filter(Dataset.id.in_(target_ids_by_category_ids))
-            return [], 0
+            else:
+                return [], 0
 
         datasets = query.paginate(page=page, per_page=per_page, max_per_page=100, error_out=False)