The navigation route disappears if you toggle the mapView's styleURL several times.

[joshpuente]

Mapbox Navigation SDK version: v0.28.0

During the turn-by-turn navigation mode we give our users the ability to toggle the mapView's styleURL. We've noticed that after doing this a few times, the blue polyline of the route disappears. However, if you continue toggling the mapView's styleUrl then eventually the blue polyline will reappear.

Steps to reproduce:

1. Start the turn-by-turn navigation mode with a particular route.
2. Change the mapView's styleURL several times during navigation
3. Notice that the route's polyline disappears

[1ec5]

We recommend specifying one or more instances of Style subclasses when initializing a NavigationViewController rather than setting styleURL directly. You can set its mapStyleURL property to the map style you want when that Style is active. The sources and style layers added by NavigationMapView.showRoutes(_:legIndex:) get blown away whenever the style URL changes, due to mapbox/mapbox-gl-native#6180, so you’d need to call NavigationMapView.showRoutes(_:legIndex:) after setting the style URL. But the Style mechanism is preferable because StyleManager already knows how to do that.