You cannot have an electoral democracy without an effective 'None of the Above' (NOTA) option.
Is it the same as leaving the circle beside all the candidates as empty or is NOTA something that forces the parties to change their platforms?
It would be an additional option on the ballot. It should be used, not just when you don't have anyone for whom you wish to vote, but if the election does not guarantee you with an adequate representative.
The election is held solely for the voter and to expect them to give their consent when they are not guaranteed adequate representation is a ludicrous situation if you think about it.
If more than 50% choose that option, the election would be re-run, and parties would have to dig into the reasons why people held their consent, and change either the candidate, or policy platforms to prevent that from happening in the re-run.
Even if the number of voters choosing NOTA did not meet that 50+% threshold, it will still provide feedback on the level of public dissatisfaction that is clear and unambiguous, which is invaluable information to those who wish to serve the public.
In future elections candidates would compete with one another to minimise the number of voters going into the NOTA bloc, so there will be a continuous pressure for good governance.
I realise I went well beyond the scope of your question, but I think the answer provides valuable background on the topic. I hope so anyway.