1) In database 1, copy a Set Variable script step that includes a valid field and comment; for example:
contacts::fName /* customer first name */
2) copy the script step and paste it into a script in another file where there is no contacts table or fName field.
3) Result: the step pastes with target variable name, but an empty calc. Normally the calc would be there but with the entire thing commented out.
'Check for Problems' function doesn't work (regardless) and there is no visible indicator that something is wrong, nothing to search for to know to manually correct it.