fix(query-sync-storage-persister): Relax undefined check against storage to handle null values (#5095)

* fix: Relax undefined check against storage to handle null values

Fixes #4957.

On Android WebView if `setDomStorageEnabled` is not configured,
`window.localStorage` will be `null` (rather than `undefined`).

Relax the existing conditional to check if `storage` is present to
handle both `null` and `undefined` values to remove a gotcha here.

* docs: update storage type

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Co-authored-by: Dominik Dorfmeister <office@dorfmeister.cc>