Not enought checks in export consensus task

If the assembly *.ugenedb file is corrupted, sometimes it is possible to start the export consensus task. This task have a subtask, that will fall in the corrupted place. The parent task doesn't check the subtask state in that case, and tries to work with incorrect operation status (it has the "failed" mark). Incorrect operation status causes several errors in the log.
Do not look at the first error on the snapshot, it is another bug.