Workflow Actions wizard; 'Index was out of range' error when reaching final page of wizard

When reaching the final page of the Worfklow Actions wizard, an 'Index was out of range' error may occur if a combination of actions such as SMS and Email have been selected.

This error only occurs if one of the lists (e.g., SMS Phone numbers) contains at least one item and the other (e.g., Email Addresses) contains no items.