No longer crash when trying to match a generic method that'll violate the generic constraints

[metoule]

Let's say you have a generic method with a generic constraint:

public T GenericMethodWithConstraint<T>(T input) where T : class
{
  return input;
}

It's invalid to call this method with an int, because it violates the generic constraints.
This PR catches any generic constraint violation, to avoid crashing.

Fixes #270

[davideicardi]

Thank you!