mariabackup.undo_space_id failed in buildbot

mariabackup.undo_space_id 'innodb'       w1 [ fail ]

        Test ended at 2020-10-24 09:49:27

CURRENT_TEST: mariabackup.undo_space_id

D:\win32-debug\build\extra\mariabackup\Debug\mariabackup.exe based on MariaDB server 10.5.7-MariaDB Win32 (AMD64)

[00] 2020-10-24 09:49:25 cd to D:\win32-debug\build\mysql-test\var\1\tmp\backup\

[00] 2020-10-24 09:49:25 This target seems to be not prepared yet.

[00] 2020-10-24 09:49:25 mariabackup: using the following InnoDB configuration for recovery:

[00] 2020-10-24 09:49:25 innodb_data_home_dir = .

[00] 2020-10-24 09:49:25 innodb_data_file_path = ib_mysql:10M

[00] 2020-10-24 09:49:25 innodb_log_group_home_dir = .

[00] 2020-10-24 09:49:25 Starting InnoDB instance for recovery.

[00] 2020-10-24 09:49:25 mariabackup: Using 104857600 bytes for buffer pool (set by --use-memory parameter)

2020-10-24  9:49:25 0 [Note] InnoDB: !!!!!!!! UNIV_DEBUG switched on !!!!!!!!!

2020-10-24  9:49:25 0 [Note] InnoDB: Uses event mutexes

2020-10-24  9:49:25 0 [Note] InnoDB: Compressed tables use zlib 1.2.11

2020-10-24  9:49:25 0 [Note] InnoDB: Number of pools: 1

2020-10-24  9:49:25 0 [Note] InnoDB: Using SSE4.2 crc32 instructions

2020-10-24  9:49:25 0 [Note] InnoDB: Initializing buffer pool, total size = 104857600, chunk size = 104857600

2020-10-24  9:49:25 0 [Note] InnoDB: Completed initialization of buffer pool

2020-10-24  9:49:25 0 [Note] InnoDB: Opened 2 undo tablespaces

2020-10-24  9:49:25 0 [Note] InnoDB: Starting crash recovery from checkpoint LSN=48161,48161

2020-10-24  9:49:25 0 [Note] InnoDB: Opened 2 undo tablespaces

2020-10-24  9:49:25 0 [Note] InnoDB: Starting final batch to recover 13 pages from redo log.

[00] 2020-10-24 09:49:26 Last binlog file , position 0

2020-10-24  9:49:26 0 [ERROR] InnoDB: File 'test\t1.ibd' has 0 operations and 1 flushes

mysqltest: At line 20: exec of 'D:\win32-debug\build\extra\mariabackup\Debug\mariabackup.exe --prepare --target-dir=D:/win32-debug/build/mysql-test/var/1/tmp/backup' failed, error: 1, status: 1, errno: 2

Output from before failure:

# xtrabackup prepare

The result from queries just before the failure was:

# Create 2 UNDO TABLESPACE(UNDO001(space_id =3), UNDO002(space_id =4))

CREATE TABLE t1(a varchar(60)) ENGINE INNODB;

start transaction;

INSERT INTO t1 VALUES(1);

# xtrabackup backup

# Display undo log files from target directory

undo001

undo002

# xtrabackup prepare

 - saving 'D:/win32-debug/build/mysql-test/var/1/log/mariabackup.undo_space_id-innodb/' to 'D:/win32-debug/build/mysql-test/var/log/mariabackup.undo_space_id-innodb/'