Return correct error when a cluster schema was not loaded

For example:

when I tried to upload a cluster schema with unsupported column type (array) to the cache, I did see any messages about errors in log file, but the schema wasn't loaded

changed milestone to %Эксплуатация

mentioned in merge request !194 (merged)

closed with merge request !194 (merged)

added 1 deleted label

added bug label

removed 1 deleted label