Remove one more potentially erroneous pltr_data check.
Remove one more potentially erroneous pltr_data check.

This was missed in my last commit.

svn path=/trunk/; revision=10896

FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot