no-op if geolocation query returns after control has been removed

[tmcw]

Launch Checklist

• Fixes Race condition between GeolocateControl and map removal #12073

As described in the linked issue, there's a race condition in which a map can be set up, a geolocate control added, and then removed before the geolocate control's query for geolocation support finishes, which will throw an error. This PR fixes that race condition by making _setupUI a no-op if the a map is no longer attached to the control.

• briefly describe the changes in this PR
• apply changelog label ('bug', 'feature', 'docs', etc) or use the label 'skip changelog'
• add an entry inside this element for inclusion in the mapbox-gl-js changelog: <changelog>Fix an issue where Geolocate control would throw an error if it's removed before determining geolocation support</changelog>

[CLAassistant]

All committers have signed the CLA.

[mourner]

Nice to see you here Tom, and thanks for the contribution!