When a new master is provisioned that does not have any old binlogs,
the @@gtid_slave_pos is used to know where in the GTID history the
provisioning happened. A slave is allowed to connect at the point of
this value of @@gtid_slave_pos, even if that GTID is not in the
binlogs on the new master.

The code to handle this case when the binlog on the newly provisioned
master is completely empty was just wrong (couple of typos). Clearly it
had never been tested ... :-/