Account for zero width line width. This happens during a replot!, and a line width of 1 is used in this case.
Account for zero width line width.
This happens during a replot!, and a line width of 1 is used in this case.

svn path=/trunk/; revision=3646

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