Suppress warning when logging is turned off
There was a case where a VTK-m exception was caught and then used in a logging message. That is fine, but if VTK-m logging is turned off, that code is removed and the exception variable goes unused. There was a time when it was common to have logging turned off in VTK-m, but now it is almost always on. There is one old-style dashboard that has logging turned off and is giving a warning about this variable not being used. It went unnoticed because the dashboard was down at the time. This should fix the issue.