(next) - Prevent restoring SSR data when client has been reset

[Biboswan]

Resolves #1714

This aims to fix two things

1. When we first visit a page and later do resetUrqlClient. We do end up using a new client because urqlClient prop was set to null. But due to ssr.restoreData(urqlServerState) Results are fetched from old ssr cache and network isn't called.
2. When we navigate to a new page (client side rendered) urqlClient prop is not null and that is the client we use. Now if you call resetUrqlClient, we don't get a new client because of existing urqlClient prop value. if (urqlClient) return urqlClient

[changeset-bot]

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Latest commit: e8fa29b

The changes in this PR will be included in the next version bump.

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Name	Type
next-urql	Patch

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[JoviDeCroock]

I've been a bit on and off about this particular issue as it introduces a very indeterministic scenario, when we have different SSG'ed pages on our web-application when reset is called these won't be able to restore anymore. Afaik server-side injecting authorized state is not really advised so logging off and on by resetting the urql-client generally won't pull data from __NEXT_DATA__ if this is done. I guess when we talk about pure SSR applications without a very strict CDN there will be cases where users store authorized state in this injected part, I would personally advise clearing the authorized state from the dom-node that injects this rather than fully clearing the client. I wouldn't incorporate this in next-urql for the reason that a lot of applications could see unexpected results.