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.
This warning was apparently introduced in !2567 (merged).