fix: ensure init_field_list defaults to an empty list in function_lib_serializer

--bug=1054092 --user=刘瑞斌 【函数库】导入历史版本的函数失败 https://www.tapd.cn/57709429/s/1678044

Author: liuruibin

apps/function_lib/serializers/function_lib_serializer.py

@@ -357,7 +357,7 @@ def import_(self, with_valid=True):
                                              code=function_lib.get('code'),
                                              user_id=user_id,
                                              input_field_list=function_lib.get('input_field_list'),
-                                             init_field_list=function_lib.get('init_field_list'),
+                                             init_field_list=function_lib.get('init_field_list', []),
                                              permission_type='PRIVATE',
                                              is_active=function_lib.get('is_active'))
             function_lib_model.save()