[vtkusers] vtkPLY exit

[James Hargrave]

Maybe it's one of my build settings or something but vtkPLY has a number of
cases where it calls exit(-1).

Is there a reason for this?  A failed return code or an exception would seem
much more useful.  As it is now when an invalid .ply file is loaded into my
application it shuts down instead of explaining the issue to the user and
just aborting the load of the file.

Any suggestions?

Thanks,
- James