[Chore/Refactor] Improve type annotations in models module (#25281)

Signed-off-by: -LAN- <laipz8200@outlook.com>
Co-authored-by: crazywoola <100913391+crazywoola@users.noreply.github.com>

api/services/app_service.py

@@ -171,6 +171,8 @@ class AppService:
         # get original app model config
         if app.mode == AppMode.AGENT_CHAT.value or app.is_agent:
             model_config = app.app_model_config
+            if not model_config:
+                return app
             agent_mode = model_config.agent_mode_dict
             # decrypt agent tool parameters if it's secret-input
             for tool in agent_mode.get("tools") or []:
@@ -205,7 +207,8 @@ class AppService:
                     pass
 
             # override agent mode
-            model_config.agent_mode = json.dumps(agent_mode)
+            if model_config:
+                model_config.agent_mode = json.dumps(agent_mode)
 
             class ModifiedApp(App):
                 """