QGLViewer keys 7 8 9(+ALT) doesn't work and eventually crash

Those keys are calling GLViewer::useDisplayParameters and GLViewer::saveDisplayParameters (GLViewerDisplay.cpp). 7 is supposed to load view settings. It crashes if no view has been saved (start yade, F10, hit "7" in the qgl view) ALT+7 to save first, then 7 to load, results in blanck screen.

Original bug report by Bruno Chareyre on 2014-10-31 : https://bugs.launchpad.net/yade/+bug/1388243