🚨 Error: Cannot read property 'querySelectorAll' of undefined

Details
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**Error report:** [link](http://go/ampe/CIOi5rTqwLXkPw)
**First seen:** Nov 24, 2020
**Frequency:** ~ 2,722/day

Stacktrace
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Error: Cannot read property 'querySelectorAll' of undefined

    at querySelectorAll (extensions/amp-next-page/1.0/service.js:695:18)

    at toggleHiddenAndReplaceableElements (extensions/amp-next-page/1.0/service.js:358:13)

    at forEach (extensions/amp-next-page/1.0/service.js:357:7)

    at updateVisibility (extensions/amp-next-page/1.0/service.js:542:13)

    at callback (extensions/amp-next-page/1.0/visibility-observer.js:310:10)

    at updateRelativePos (extensions/amp-next-page/1.0/visibility-observer.js:109:19)

    at handler_ (src/service/position-observer/position-observer-worker.js:109:11)

Notes
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`@renovate-bot` modified `extensions/amp-next-page/1.0/service.js:695-695` in [#27350](https://github.com/ampproject/amphtml/pull/27350) (Mar 30, 2020)
`@wassgha` modified `extensions/amp-next-page/1.0/service.js:358-358` in [#26106](https://github.com/ampproject/amphtml/pull/26106) (Jan 13, 2020)
`@renovate-bot` modified `extensions/amp-next-page/1.0/service.js:356-357` in [#27350](https://github.com/ampproject/amphtml/pull/27350) (Mar 30, 2020)
`@wassgha` modified `extensions/amp-next-page/1.0/service.js:541-545` in [#26296](https://github.com/ampproject/amphtml/pull/26296) (Jan 23, 2020)
`@wassgha` modified `extensions/amp-next-page/1.0/visibility-observer.js:294-381` in [#26778](https://github.com/ampproject/amphtml/pull/26778) (Apr 9, 2020)
`@wassgha` modified `extensions/amp-next-page/1.0/visibility-observer.js:109-109` in [#26778](https://github.com/ampproject/amphtml/pull/26778) (Apr 9, 2020)
`@zhouyx` modified `src/service/position-observer/position-observer-worker.js:106-136` in [#10813](https://github.com/ampproject/amphtml/pull/10813) (Sep 8, 2017)

**Seen in:**
- 03-02 Nightly-Control (0156+5)
- 03-06 Beta (0631+2)
- 03-06 Experiment-B (0631+2)
- 03-06 Experimental (0631+2)
- +13 more

**Possible assignees:** `@wassgha`, `@zhouyx`

/cc @ampproject/release-on-duty