in src/AzureAppConfigurationImpl.ts [846:852]
function getValidKeyValueSelectors(selectors?: SettingSelector[]): SettingSelector[] {
if (selectors === undefined || selectors.length === 0) {
// Default selector: key: *, label: \0
return [{ keyFilter: KeyFilter.Any, labelFilter: LabelFilter.Null }];
}
return getValidSelectors(selectors);
}