* lisp/erc/erc-track.el (erc-track-modified-channels): Fix what is a
probable bug when a new insert event happens for a buffer that was not
tracked or for which no mode line face was selected: in this case,
stop treating the latest buffer's face (first in list) as the previous
one, which could be overridden with an older one (in FACES' rest), as
if it had happened after.