fix: handle 'None' string in field value checks

Author: liuruibin

apps/application/flow/step_node/search_document_node/impl/base_search_document_node.py

@@ -120,7 +120,7 @@ def handle_custom_tags(self, document_id_list: List, search_condition_list: list
                 field_value = self.workflow_manage.generate_prompt(condition['value'])
                 compare_type = condition['compare']
 
-                if not field_value or len(field_value) == 0:
+                if not field_value or field_value == 'None' or len(field_value) == 0 :
                     continue
 
                 # 构建查询条件
@@ -159,7 +159,7 @@ def handle_custom_tags(self, document_id_list: List, search_condition_list: list
                 field_value = self.workflow_manage.generate_prompt(condition['value'])
                 compare_type = condition['compare']
 
-                if not field_value or len(field_value) == 0:
+                if not field_value or field_value == 'None' or len(field_value) == 0 :
                     continue
 
                 if compare_type == 'not_contain':