Issue #3332244 - TypeError getNoPreferredIndexError() argument type error

When local credentials are not, an object of class AcquiaSearchSolrApi with empty properties will be created in getFromSettings(). So $preferred_index will be empty. This will cause a false alarm of AcquiaSearchSolrMessages::getNoPreferredIndexError($preferred_core_service->getAvailableCoreIds()).