fix: default model set wrong（#6327） (#6332)

Co-authored-by: maiyouming <maiyouming@yafex.cn>

api/services/app_service.py

                 model_instance = None
 
             if model_instance:
-                if model_instance.model == default_model_config['model']['name']:
+                if model_instance.model == default_model_config['model']['name'] and model_instance.provider == default_model_config['model']['provider']:
                     default_model_dict = default_model_config['model']
                 else:
                     llm_model = cast(LargeLanguageModel, model_instance.model_type_instance)