<!-- Welcome! Before creating a new issue: * Search for relevant issues * Follow the issue reporting guidelines: https://jupyterlab.readthedocs.io/en/latest/getting_started/issue.html --> ## Description When opening the slideshow with Jupyter Notebook 7.3.2:  ## Reproduce Open a notebook with Jupyter Notebook 7.3, then open in slideshow mode. ## Expected behavior  ## Context - `jupyterlab-slideshow==0.3.0` - `notebook==7.3.2`