Cursor protocol gives incorrect result with the utf8mb4 character set in COLUMN_LIST function

Testcase (run MTR test with --cursor-protocol):

SET NAMES utf8mb4;

SELECT COLUMN_LIST(COLUMN_CREATE(_utf8mb4 0xF09F9982, 1));

Expected result:
COLUMN_LIST(COLUMN_CREATE(_utf8mb4 0xF09F9982, 1))
``

Actual result:
COLUMN_LIST(COLUMN_CREATE(_utf8mb4 0xF09F9982, 1))
`????`