[Bug] multi-turn error on browser use demo

[zzhangpurdue]

Security Issues: If this involves security vulnerabilities, report via Alibaba Security Response Center (ASRC) instead of creating a public issue.

Bug Description

after one round chat, an attribute error will be thrown immediately, when ask any following question.

Affected Component

• Engine
• Sandbox
• Documentation
• Other:Demos___

Reproduction Steps

1. Your code: [paste code here]
2. How to run: [command used] follow the browser use demos setup
3. Error occurs at: [describe when]

Expected vs Actual Behavior

Expected: [what should happen]
Actual: [what actually happened]

Error Messages

[Paste full error messages/stack traces]

Environment

• AgentScope Runtime Version: [e.g. v0.1.0]
• Python Version: [e.g. 3.10]
• OS: [e.g. Ubuntu 20.04]
• Installation: [pip/source]

Additional Context

[Any other relevant information]

[zhilingluo]

it's known bug in AgentscopeAgent class. To be fixed.