get_latest_quakes_chis_fsdn_site(initial_target, target_centres) does not gracefully handle API connection errors

[drotheram]

When the dashboard can't communicate with the API target_centers is populated with the following dict:
{'API Response Error': [50.64, -123.6]}
However initial_target is populated with the following:
Meager_5M3

get_latest_quakes_chis_fsdn_site(initial_target, target_centres) will throw an error because that target is not in the target_centers dict when there is an API connection error.

Modify this function to gracefully handle this exception and keep running