Generated images don't display in Jupyter Lab

[nalzok]

Take the example of 0_demo.ipynb:

Inspect Element gives the following HTML output

<img src="http://localhost:8888/files/%20build/MovingAverage368251718.dot.svg?_xsrf=2%7Cb4c0efbf%7C0f080edcfcae8c04d70c24d5ae5b69a7%7C1590588518&amp;1590637312836" alt="Module View" ;"="">

Apparently the path files/build is mistyped as files/%20build. The bug doesn't manifest itself when I use Jupyter Notebook. I'm not sure if it's a bug of Jupyter Lab or this repository.

This issue is cross-posted at jupyterlab.