Fix bugs in handling transformations of zero-length or completely blank character strings.
Fix bugs in handling transformations of zero-length or completely blank
character strings.

svn path=/trunk/; revision=5074

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