修复样本中心接口问题

backend/app/schemas/sample_center.py

@@ -1,17 +1,22 @@
-from pydantic import BaseModel
+from pydantic import BaseModel, field_validator
 
 
 class KnowledgeBaseItem(BaseModel):
     id: str
     name: str
-    parent_table: str
-    child_table: str
+    parent_table: str = ""
+    child_table: str = ""
     document_count: int
     status: str
     created_at: str
     created_by: str
     metadata_schema: list[dict] = []
 
+    @field_validator("parent_table", "child_table", mode="before")
+    @classmethod
+    def none_to_empty(cls, v: str | None) -> str:
+        return v if v is not None else ""
+
 
 class KnowledgeBaseListResponse(BaseModel):
     total: int
@@ -24,8 +29,8 @@ class KnowledgeBaseDetailResponse(BaseModel):
     id: str
     name: str
     description: str = ""
-    parent_table: str
-    child_table: str
+    parent_table: str = ""
+    child_table: str = ""
     document_count: int
     status: str
     created_at: str
@@ -33,6 +38,11 @@ class KnowledgeBaseDetailResponse(BaseModel):
     created_by: str
     metadata_schema: list[dict] = []
 
+    @field_validator("parent_table", "child_table", mode="before")
+    @classmethod
+    def none_to_empty(cls, v: str | None) -> str:
+        return v if v is not None else ""
+
 
 class ImportTaskResponse(BaseModel):
     task_id: str
@@ -44,5 +54,10 @@ class KbImportResponse(BaseModel):
     kb_name: str
     document_count: int
     metadata_schema: list[dict] = []
-    parent_table: str
-    child_table: str
+    parent_table: str = ""
+    child_table: str = ""
+
+    @field_validator("parent_table", "child_table", mode="before")
+    @classmethod
+    def none_to_empty(cls, v: str | None) -> str:
+        return v if v is not None else ""