crashes with invalid gnuplot syntax

[George Shuklin]

$ battery-graph

gnuplot> set ylabel "%Full" 0.000000,0.000000
                            ^
         "/usr/share/battery-stats/graph-setup", line 35: unexpected or unrecognized token

         line 0: warning: Skipping data file with no valid points

gnuplot> plot "-" using ($1 - 946674000):2 smooth unique axis x1y1 title "Battery %" with lines linewidth 3
                                                                                                           ^
         line 0: all points y value undefined!

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: battery-stats 0.3.6-1
ProcVersionSignature: Ubuntu 4.4.0-18.34-generic 4.4.6
Uname: Linux 4.4.0-18-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CurrentDesktop: X-Cinnamon
Date: Wed Apr 27 05:14:27 2016
EcryptfsInUse: Yes
InstallationDate: Installed on 2013-07-19 (1012 days ago)
InstallationMedia: Xubuntu 13.04 "Raring Ringtail" - Release i386 (20130423.1)
SourcePackage: battery-stats
UpgradeStatus: Upgraded to xenial on 2015-10-29 (180 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.