fix: 知识库添加时 vec 变量未初始化导致 embedding 禁用时报错

src/knowledge_base/knowledge_manager.py

@@ -356,6 +356,7 @@ class KnowledgeManager:
 
             # 生成 embedding
             embedding_json = None
+            vec = None
             text_for_embedding = question + " " + answer
             if self.embedding_enabled:
                 vec = self.embedding_client.embed_text(text_for_embedding)