bug 14453 fix for stream tracer

per http://www.vtk.org/Bug/view.php?id=14453

thanks Jorge for the patch

Change-Id: Ief67c8224f1d39b2c918bf24d3f4f347ee5a3835
Merge topic '0014453-fix-for-streamtracer' into master

921fac16 bug 14453 fix for stream tracer