I can now confirm that this crash is FIXED in the next Modo release (12.1v1) combined with with the next Modo plugin release built with Octane 3.08.2. The plugin release built with Octane 3.08.1 still results in a crash.
OTOY have provided a patch for 3.08.1, so this should now be resolved with the 3.08.1.131, which I will release later this week (if you are using the latest Modo beta).