Like the error in
CASSANDRA-12213 and CASSANDRA-12165, it's possible for system_schema.keyspaces and tables to contain entries for a table while system_schema.columns has none. This produces an error during startup, and there's no way for a user to recover from this without restoring from backups.
Although this has been seen in the wild on one occasion, the cause is still not entirely known. (It may be due to a concurrent DROP TABLE and ALTER TABLE where a table property is altered.) Until we know the root cause, it makes sense to give users a way to recover from that situation.