getMaxPage assumes nbPages is always a number

[tkrugg]

Describe the bug 🐛

getMaxPage assumes nbPages is always a number. This is nolonger true in 4.0.0 as it can be undefined

To Reproduce 🔍

Steps to reproduce the behavior:

1. Download an run: https://github.com/algolia/doc-code-samples/tree/master/InstantSearch.js/conditional-request
2. In index.html, update instantsearch source script to @4.0.0
3. Reload
4. See error

Uncaught (in promise) RangeError: Invalid array length

A live example helps a lot! We have a simple online template for you to use for your explanations:

https://codesandbox.io/s/conditional-request-n2cw3

Other widgets assume nbPages is a number:

• InfiniteHits: https://github.com/algolia/instantsearch.js/blob/b454759f513b8681e5c7efd677b0b79da5fac137/src/connectors/infinite-hits/connectInfiniteHits.ts#L189
• Stats: for nbPages and maybe nbHits https://github.com/algolia/instantsearch.js/blob/b454759f513b8681e5c7efd677b0b79da5fac137/src/components/Stats/Stats.js#L29 (people customizing might start getting NaNs)
• Make sure we check for nbHits, page and hitsPerPage.

Expected behavior 💭 No errors

Screenshots 🖥 N/A

Environment:

• OS: mac
• Browser: chrome
• Version: 78

Additional context N/A

[Haroenv]

https://github.com/algolia/instantsearch.js/blob/8feef58c7c8e7b7b1b213d5ed70206304c2c10ed/src/connectors/pagination/connectPagination.ts#L89

this should become

      getMaxPage({ nbPages = 0 }) {

or a similar solution then I guess

[Haroenv]

Actually this is in the contract of the API that nbPages, nbHits, page and hitsPerPage are always returned and a number. Therefore conditional fake responses should have those keys as well, and our documentation includes those keys already.

No further action is needed as this didn't come up for other people.