It has now been confirmed that the online voting system does allow a spoilt ballot ‘paper’.

But with all this technology is it still possible to get it wrong?
Yes explained Mr Winchcombe
[Swindon deputy returning officer]. By failing to select any candidate on screen or by voting for more than one candidate.
“But you will get a warning on screen asking if this is really what you want to do though,” he added.

It’s nice to know that the option of last resort is still available.