EuiComboBox throws an exception "randomly"

[timroes]

I triggered this somehow in the very basic EuiComboBox example in the docs when adding some custom options.

I can't reproduce this reliable, but maybe knowing the code is enough to figure out what the issue is:

combo_box_options_list.js:54 Uncaught TypeError: Cannot read property 'getBoundingClientRect' of null
    at combo_box_options_list.js:54

[chandlerprall]

The getBoundingClientRect has since been refactored out, and there is a defensive check in an upstream use of this code path.