fixed condition to determine no overlap

Author: EduardRosert

src/visualisers/IsoPlot.cc

@@ -1206,7 +1206,7 @@ void IsoPlot::isoline(MatrixHandler& data, BasicGraphicsObjectContainer& parent)
     // If data range has no overlap with the level range, the levels loop below
     // would produce a single artificial band [last_level, data_max] covering
     // every grid point, causing O(N) polygon segment allocation for all N cells.
-    if (max <= (*levelSelection_).front() || min >= (*levelSelection_).back())
+    if (max < (*levelSelection_).front() || min > (*levelSelection_).back())
         return;
 
     if ((*levelSelection_).front() > min)