🚨 Error: null is not an object (evaluating 'h.style')

Details
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**Error report:** [link](http://go/ampe/CN7xqYeTzJ6VDw)
**First seen:** Jun 7, 2021
**Frequency:** ~ 9,697/day

Stacktrace
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Error: null is not an object (evaluating 'h.style')

    at style (src/core/dom/style.js:121:10)

    at mutator (src/service/mutator-impl.js:221:8)

    at state (src/service/vsync-impl.js:471:25)

    at tasks (src/service/vsync-impl.js:428:18)

Notes
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`@rsimha` modified `src/core/dom/style.js:120-124` in [#21212](https://github.com/ampproject/amphtml/pull/21212) (May 16, 2019)
`@powerivq` modified `src/service/mutator-impl.js:219-221` in [#26638](https://github.com/ampproject/amphtml/pull/26638) (Feb 12, 2020)
`@jridgewell` modified `src/service/vsync-impl.js:471-472` in [#20836](https://github.com/ampproject/amphtml/pull/20836) (Feb 14, 2019)
`@rsimha` modified `src/service/vsync-impl.js:428-428` in [#23363](https://github.com/ampproject/amphtml/pull/23363) (Jul 17, 2019)

**Seen in:**
- 07-17 Stable (0150)
- 07-24 Beta (0354)
- 07-24 Control (0354)
- 07-24 Experiment-B (0354)
- 07-24 Nightly-Control (0354)
- 08-04 Nightly (0347)
- +3 more

**Possible assignees:** `@powerivq`, `@rsimha`

/cc @ampproject/release-on-duty

Start with src/core/dom/style.js:121 and trace the call chain through src/service/mutator-impl.js:221 and src/service/vsync-impl.js:471,428. Use the linked stack trace and referenced pull requests to determine how a null element reaches style(). Done means the production error has a confirmed cause, a targeted fix is identified, and a regression test or reproduction verifies the failure no longer occurs.

Written by the indexing model from the issue text.