Fix: make isclock robust to non TimeDomain argument

[pitx-perf]

Tentative to fix: #945

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

Add any other context about the problem here.

[AayushSabharwal]

Thanks for the quick fix. This looks good if tests pass. It seems the issue is because Moshi uses the function Moshi.Data.isa_variant to check if a given object is the specified ADT variant, but the function is not robust to arguments that aren't a variant of the ADT.