🚨 Error: null is not an object (evaluating 'a.__AMP_TOP')

Details
---
**Error report:** [link](http://go/ampe/CNaM9qq564jGGQ)
**First seen:** Nov 27, 2020
**Frequency:** ~ 386/day

Stacktrace
---

Error: null is not an object (evaluating 'a.__AMP_TOP')

    at __AMP_TOP (src/service.js:291:13)

    at win (src/service.js:153:21)

    at getService (src/service.js:344:62)

    at elementOrAmpDoc (src/service.js:217:27)

    at elementOrAmpDoc (src/services.js:797:6)

    at src/service/resource.js:671:45

    at r (src/service/resources-impl.js:1281:32)

    at doWork (src/service/resources-impl.js:1864:6)

    at callback (src/finite-state-machine.js:72:6)

    at src/service/resources-impl.js:783:42

    at src/service/resources-impl.js:142:42

    at src/pass.js:109:4

    at src/pass.js:55:6

    at callback (src/service/timer-impl.js:79:10)

Notes
---
`@cramforce` modified `src/service.js:291-291` in [#23767](https://github.com/ampproject/amphtml/pull/23767) (Aug 7, 2019)
`@choumx` modified `src/service.js:147-156` in [#10131](https://github.com/ampproject/amphtml/pull/10131) (Jun 28, 2017)
`@rsimha` modified `src/service.js:344-347` in [#21212](https://github.com/ampproject/amphtml/pull/21212) (May 16, 2019)
`@choumx` modified `src/service.js:212-221` in [#16328](https://github.com/ampproject/amphtml/pull/16328) (Jun 29, 2018)
`@rsimha` modified `src/services.js:797-799` in [#21212](https://github.com/ampproject/amphtml/pull/21212) (May 16, 2019)
`@lannka` modified `src/service/resource.js:671-671` in [#23313](https://github.com/ampproject/amphtml/pull/23313) (Jul 18, 2019)
`@lannka` modified `src/service/resources-impl.js:1864-1864` in [#24622](https://github.com/ampproject/amphtml/pull/24622) (Sep 20, 2019)
`@jridgewell` modified `src/finite-state-machine.js:63-78` in [#1637](https://github.com/ampproject/amphtml/pull/1637) (Mar 18, 2016)
`@dvoytenko` modified `src/service/resources-impl.js:783-783` in [#24566](https://github.com/ampproject/amphtml/pull/24566) (Sep 20, 2019)
`@jridgewell` modified `src/service/resources-impl.js:142-142` in [#9789](https://github.com/ampproject/amphtml/pull/9789) (Jun 8, 2017)
`@jridgewell` modified `src/pass.js:105-112` in [#3513](https://github.com/ampproject/amphtml/pull/3513) (Jun 9, 2016)
`@rsimha` modified `src/pass.js:50-56` in [#23559](https://github.com/ampproject/amphtml/pull/23559) (Jul 29, 2019)
`@rsimha` modified `src/service/timer-impl.js:73-81` in [#21212](https://github.com/ampproject/amphtml/pull/21212) (May 16, 2019)

**Seen in:**
- 01-21 Control (1748+1)
- 01-21 Control (1748+2)
- 01-21 Experimental (1748+1)
- 01-21 Experimental (1748+2)
- 01-21 Nightly-Control (1748+2)
- 01-21 Stable (1748+1)
- +4 more

**Possible assignees:** `@lannka`, `@cramforce`

/cc @ampproject/release-on-duty

Start with the linked stack trace and inspect src/service.js at lines 147-156, 291, and 344, then follow the calls through src/services.js, src/service/resource.js, and src/service/resources-impl.js. Use the error-report link and listed production occurrences to investigate when the null value reaches __AMP_TOP. Done means the cause is identified and the error is no longer reproducible or is handled safely.

Written by the indexing model from the issue text.