Fix imac compile errors and runtime raster warnings

These patches fix some issues with the new raster code so that hcana will compile under MacOS and so that it won't give the warning:

"Warning in <TVector3::SetMag>: zero vector can't be stretched"

for every event.

These changes do not purport to improve the raster code and may break functionality.  They simply allow hcana to compile on MacOS and not print warnings at run time.