Pressing power button causes a blank figure

Pressing the power button (toggle interaction) causes the whole figure to become blank, instead of just disabling interaction. Difficult to reproduce this every time. Tried with both Firefox and Chrome, and in some cases (mostly Firefox), the button worked as intended. In some cases the plot line is still visible, but the axes and labels disappear.

Tested on jupyter lab. My versions are the following:

```
matplotlib 2.2.2 py36_1 conda-forge
ipympl 0.2.1 py36_0 conda-forge
jupyter_client 5.2.3 py_1 conda-forge
jupyter_core 4.4.0 py_0 conda-forge
jupyterlab 0.32.1 py36_0 conda-forge
jupyterlab_launcher 0.10.5 py36_0 conda-forge
@jupyter-widgets/jupyterlab-manager
@jupyter-widgets/jupyterlab-manager v0.35.0 enabled OK
Firefox 61.0.1
Chrome 67.0.3396.99
```

Start by reproducing the power-button toggle in JupyterLab using the listed Firefox and Chrome versions, then compare cases where the plot becomes blank with cases where it works. Done means disabling interaction leaves the plot line, axes, and labels visible instead of blanking or partially hiding the figure.

Written by the indexing model from the issue text.