Contour throws exceptions when trying to infer x and y axis types after switching from numerical to category.

[mcin-armintaheri-archive]

http://codepen.io/armintaheri/pen/NrGLxY

When plotting a contour plot with x-axis set to a numerical array, then calling restyle with a categorical array, then calling relayout with {'xaxis.type': '-'}, The following exceptions are thrown:

Error: <path> attribute d: Expected number, "M,0L,0L,270L,270Z".
Uncaught TypeError: Cannot read property '0' of undefined

And the plot does not change its axis type.

[etpinard]

Strange. Restyling a categorical x to a linear type works fine.

Thanks for reporting.

[etpinard]

This bug is still present in 1.20.x, but at least now a workaround : replacing restyle + relayout by Plotly.update works as desired.

[etpinard]

Potentially fixed in #1999 cc @alexcjohnson