Cannot read property 'length' of undefined

[brubbel]

Description:
Background updates using Plotly.redraw(), while zooming on a plot produce the following error:
Uncaught TypeError: Cannot read property 'length' of undefined

Test case
http://jsfiddle.net/gq9zrhd4/
The plot is updated every second, so start a box zoom and the errors appear.

(It is possible that this way of updating is not allowed, so is there a correct way to zoom into a (big) plot which is still loading in the background?)

Browser: Chrome Version 68.0.3440.106 (Official Build) (64-bit)

[etpinard]

Probably a duplicate of #2687

[etpinard]

Merging with #2687