'dctx' must be non NULL, remove test.

'dctx' must be non NULL, remove test.

1549 cleanup:
1550        if (dctx->dbiter != NULL)
1551                dns_dbiterator_destroy(&dctx->dbiter);
1552        if (dctx->db != NULL)
1553                dns_db_detach(&dctx->db);

	CID 1452686 (#1 of 1): Dereference before null check (REVERSE_INULL)
	check_after_deref: Null-checking dctx suggests that it may
	be null, but it has already been dereferenced on all paths
	leading to the check.

1554        if (dctx != NULL)
1555                isc_mem_put(mctx, dctx, sizeof(*dctx));