and replicated):

A DROP USER statement with a non-existing user was correctly written to
the binary log (there might be users that were removed, but not all),
but the error code was not set, which caused the slave to stop with an
error.

The error reporting code was moved to before the statement was logged
to ensure that the error information for the thread was correctly set
up. This works since my_error() will set the fields net.last_errno and
net.last_error for the thread that is reporting the error, and this
will then be picked up when the Query_log_event is created and written
to the binary log.