We have this error since we've upgraded from 5.x to 6.x today, may be upstream or not. Must be Translate's TranslationStats, I can't think how useroptionstats could produce it.
-rakkaus:#mediawiki-i18n- (1 lines skipped) [24-Mar-2014 14:33:08 UTC] PHP Fatal error: SetPlotAreaWorld(): Y range error - min >= max
in /home/betawiki/software/phplot-6.1.0/phplot.php on line 1957
Version: master
Severity: normal