Fail to react to tiles in mapbox.style.sources

[archmoj]

Originally reported in plotly/dash#1152.
MINIMAL DEMO

[archmoj]

Not clear what is going on here.

[archmoj]

In order for the example to work, this line

plotly.js/src/plots/mapbox/mapbox.js

Line 62 in d37895b

if(self.map && (opts.accesstoken !== self.accessToken)) {

could be

if(self.map) {

So there might be a problem clearing access token for open/free maps.