Currently, the client fails hard with an exception if the sites table is empty or a site not found.
Exception from line 463 of
Unable to resolve site ID 'enwiki'!
We need to handle this more gracefully and at the same time log it in a prominent way that we are sure to be notified and aware.
An unknown site id could happen, for example, if there is a new wikipedia added and the sites data is not synched fully yet across the clients and repo, among other plausible scenarios.