Uncaught TypeError while zooming during extendTraces

[galuha]

Hello.
The problem is, when zooming with the mouse selection while Plotly is doing extendTraces, it throws this "Uncaught TypeError: Cannot read property 'length' of undefined".
To reproduce, try to zoom the chart, i.e. select some area and hold the selection for a while. The error will be visible in the browser console

https://codepen.io/galuha/pen/ywMmPZ?editors=1111

[archmoj]

@galuha Thanks for the report as well as clear codepen.

[etpinard]

Essentially a duplicate of #3305