the only query of the XA transaction is on a non-transactional table
errors out:

XA BEGIN 'x';
--error ER_DUP_ENTRY
INSERT INTO t1 VALUES (1),(1);
XA END 'x';
XA PREPARE 'x';

The binlogging pattern is correctly started as expected with
the errored-out Query or its ROW format events, but there is
no empty XA_prepare_log_event group.
The following

XA COMMIT 'x';

therefore should not be logged either, but it does.

The bug is fixed with proper maintaining of a read-write binlog hton
property and use it to enforce correct binlogging decisions.
Specifically in the bug description case XA COMMIT won't be binlogged
in both when given in the same connection and externally after disconnect.
The same continue to apply to an empty XA that do not change any data in all
transactional engines involved.