as discussed in #95 this simple change should make layers persistent for all edge cases
logic before: if source does not exist, addLayer whenever source is being reloaded (ex. on map style change)
logic now: addLayer whenever source is being reloaded
as discussed in #95 this simple change should make layers persistent for all edge cases
logic before: if source does not exist, addLayer whenever source is being reloaded (ex. on map style change) logic now: addLayer whenever source is being reloaded