以界面模式启动，程序未响应后关闭重新启动，无法显示出界面

**Summary[问题简述（一句话）]**
以界面模式启动，程序未响应后关闭重新启动，无法显示出界面

**Env & To Reproduce[复现与环境]**
python3.7.9
`python demo_toolbox.py -d dataset` 以界面模式启动后，点击 load above 然后在右侧输入框输入文字时候卡住，程序未响应。关闭后再次启动程序则不出现界面。

**Screenshots[截图（如有）]**

再次启动会卡在这里

Start with demo_toolbox.py using `python demo_toolbox.py -d dataset`, then reproduce the freeze after clicking “load above” and typing in the right-side input. Investigate why the interface stops responding and why a subsequent launch shows no interface; done means the interface remains usable and can be relaunched after closing.

Written by the indexing model from the issue text.