bind: Crash from assertion error when debug log level is 10 and log entries meet buffer boundary

While backporting a feature for a newer branch of BIND9, RedHat introduced a path leading to an assertion failure in buffer.c:420. Affects RedHat versions bind-9.9.4-65.el7 - bind-9.9.4-72.el7. No ISC releases are affected. Other packages from other distributions who made the same error may also ...