When passing View arguments using token values, it could be a single value or multiple values. For example, if you have multiple taxonomy term IDs like NULL/NULL/7876, you will need to pad the empty values with null if they are optional. This will still allow the view to respect the only filter. But if you had NULL/NULL/NULL, then no results will be shown from the view. I was able to solve this issue by setting empty values as 'NULL' and then checking to see if only those values, if only NULL values were defined, then I would just pass along an empty array which allows the view to render content without any contextual filters applied.
Needs work
2.1
Code