parse: get rid of raw option offsets

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/options.c b/options.c
index 29b181a..5ee70be 100644
--- a/options.c
+++ b/options.c
@@ -3786,7 +3786,13 @@
 		__o++;
 	}
 
+	if (opt_index + 1 == FIO_MAX_OPTS) {
+		log_err("fio: FIO_MAX_OPTS is too small\n");
+		return 1;
+	}
+
 	memcpy(&fio_options[opt_index], o, sizeof(*o));
+	fio_options[opt_index + 1].name = NULL;
 	return 0;
 }