Change value sent for 'None of the above' option for conditions

[SamJamCul]

What problem does this pull request solve?

https://trello.com/c/2H6cVned/2228-routes-based-on-none-of-the-above-answers-do-not-work

This reconciles a bug which we've encountered in forms runner - where we've been saving the answer value for optional selection questions as none_of_the_above, which will not be sucessfully compared with the forms runner's value of None of the above.

The change in the API is to make sure that our answer value doesn't exist error is now looking for a value of None of the above when it's an optional question, rather than none_of_the_above.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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