♻️ refactor: change empty content stream behavior

[hezhijie0327]

💻 变更类型 | Change Type

• ✨ feat
• 🐛 fix
• ♻️ refactor
• 💄 style
• 👷 build
• ⚡️ perf
• 📝 docs
• 🔨 chore

🔀 变更说明 | Description of Change

从 #3392 中拆分，Stream 流中 content 为空的处理行为

情况如下：
当 tool_calls 存在，但 content 为空字符串，引起 UI 对话界面显示空，但无报错

📝 补充信息 | Additional Information

{"choices":[{"index":0,"message":{"role":"assistant","content":"","tool_calls":[{"id":"3NcHNntdRyaHu8zisKJAhQ","function":{"name":"realtime-weather____fetchCurrentWeather","arguments":"{\"city\": \"Singapore\"}"}}]},"stop_reason":"tool_calls"}]}

[vercel]

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[lobehubbot]

👍 @hezhijie0327

Thank you for raising your pull request and contributing to our Community
Please make sure you have followed our contributing guidelines. We will review it as soon as possible.
If you encounter any problems, please feel free to connect with us.
非常感谢您提出拉取请求并为我们的社区做出贡献，请确保您已经遵循了我们的贡献指南，我们会尽快审查它。
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.83%. Comparing base (fdaa190) to head (713ffa4).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##             main    #3883     +/-   ##
=========================================
  Coverage   91.83%   91.83%             
=========================================
  Files         455      455             
  Lines       30445    30452      +7     
  Branches     1963     3105   +1142     
=========================================
+ Hits        27958    27965      +7     
  Misses       2487     2487             

Flag	Coverage Δ
app	91.83% <100.00%> (+<0.01%)	⬆️
server	97.36% <ø> (ø)

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[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
lobe-chat-preview	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 10, 2024 1:58pm

[lobehubbot]

❤️ Great PR @hezhijie0327 ❤️

The growth of project is inseparable from user feedback and contribution, thanks for your contribution! If you are interesting with the lobehub developer community, please join our discord and then dm @arvinxx or @canisminor1990. They will invite you to our private developer channel. We are talking about the lobe-chat development or sharing ai newsletter around the world.
项目的成长离不开用户反馈和贡献，感谢您的贡献! 如果您对 LobeHub 开发者社区感兴趣，请加入我们的 discord，然后私信 @arvinxx 或 @canisminor1990。他们会邀请您加入我们的私密开发者频道。我们将会讨论关于 Lobe Chat 的开发，分享和讨论全球范围内的 AI 消息。

[lobehubbot]

🎉 This PR is included in version 1.15.34 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[abix5]

I checked on the latest (v1.17.0) version, the bug persists

v1.15.31 works great

[hezhijie0327]

@abix5 can create a new issue and share the stream?