Virtualized cells not displayed after hot-reloading

[chriddyp]

This is hard for me to reproduce, but I'm seeing that the dash-table virutalization cells aren't always displayed when working locally in the docs. Here's a screenshot:

Doing a hard reload will fix the issue sometimes.

[chriddyp]

cc @Marc-Andre-Rivet

[chriddyp]

To reproduce:

1. Run the dash docs in Firefox

2. Open up http://localhost:8060/datatable/virtualization
   

3. Make some changes to your code so that a hot-reload is triggered

4. Notice how the table might not render
   

5. Do a hard-reload (cmd-shift-r) and notice how it appears