Fixed a bug causing material related segmentation fault when running cmgui/libzinc in rare occasions. https://tracker.physiomeproject.org/show_bug.cgi?id=3726
Fixed a bug causing material related segmentation fault when running cmgui/libzinc in rare occasions. https://tracker.physiomeproject.org/show_bug.cgi?id=3726

git-svn-id: b9baf8c2d14a71b3ba9c27a102eb6e792fc13348@10871 3c1deb5b-d424-0410-962d-aba41a686d42

OpenCMISS/zinc,hsorby/zinc,OpenCMISS/zinc,hsorby/zinc,OpenCMISS/zinc,OpenCMISS/zinc,hsorby/zinc,hsorby/zinc