fix(HistogramSelector): fix negative width error.
fix(HistogramSelector): fix negative width error.

Score region rects could get a negative width when
the score histogram changed to zero width. Make
getRegionBound return [0,1] in that case, to avoid
the error.

Kitware/paraviewweb,Kitware/paraviewweb,Kitware/paraviewweb,Kitware/paraviewweb