Fix bug when assurance question is not answered
Fix bug when assurance question is not answered

If a user tries to save a page but doesn't answer all the assurance questions the following error occurs:

```
argument of type 'NoneType' is not iterable
```

This commit updates the version of the toolkit to include
https://github.com/alphagov/digitalmarketplace-frontend-toolkit/pull/132

…which fixes this issue.

alphagov/digitalmarketplace-supplier-frontend,alphagov/digitalmarketplace-supplier-frontend,alphagov/digitalmarketplace-supplier-frontend,alphagov/digitalmarketplace-supplier-frontend