Segmentation fault with COMPUTEPERCENTILES

COMPUTEPERCENTILES gives a segmentation fault when all particles die during the simulation. It can happen when the whole beam collides with the geometry, by particle-matter interaction or by interaction with interceptive elements (stripper, collimator...).

A simple way to reproduce the bug is to run GasStripping regression test increasing the pressure level enough to achieve total particle loss (PRESSURE=1.0e-1) with OPTION, COMPUTEPERCENTILES=TRUE;