Lowest colormap color is set to white when chart type is changed to contour

[Fredx87]

When updating chart data and setting type to "contour", the lowest color in the colormap is always set to white instead of the right color.

This is a reproduction on codepen: https://codepen.io/fredx87/pen/YzqdJZz

If I use Plotly.react the colorbar is wrong, if I redraw the chart using Plotly.newPlot the colorbar is correct.

[archmoj]

Thanks for the report and clear demo.

[anaplian]

I've had a go at this in #5217
Let me know if that's OK 😄

Happy Hacktoberfest! 🎃