Notice: Undefined variable: head

I'm getting the notice

Notice: Undefined variable: head in include() (line 50 of / .../ .../ ...l/.../modules/system/html.tpl.php)

(.../ is actually address replacement)

It appeared after a cron run, not sure if that has anything to do with it, but it is at the very least curious (this had been on automatic check every 3 hrs or whatever the default was, I have since set it to manual)

TYPE cron
DATE Tuesday, October 20, 2015 - 4:16am
USER Anonymous (not verified)
LOCATION http://www......com/
REFERRER http://www......com
MESSAGE Cron run completed.
SEVERITY notice
HOSTNAME 83.5.99.146
OPERATIONS

All modules are up to date, with the exception of core(happening this weekend), and the error is there with and without the updates.

Running PHP ver 5.4

Originally posted https://www.drupal.org/node/2599748 and referred here