🚨 Error: Cannot read property 'timeStamps' of undefined

Details
---
**Error report:** [link](http://go/ampe/CP3ipp6vp7bC1AE)
**First seen:** Jul 31, 2020
**Frequency:** ~ 964/day

Stacktrace
---

Error: Cannot read property 'timeStamps' of undefined

    at timeStamps (extensions/amp-story/1.0/media-performance-metrics-service.js:413:11)

    at localListener (src/event-helper-listen.js:58:13)

Notes
---
`@gmajoulet` modified `extensions/amp-story/1.0/media-performance-metrics-service.js:413-422` in #23962 (Aug 20, 2019)
`@rsimha` modified `src/event-helper-listen.js:57-59` in #12450 (Dec 13, 2017)

**Seen in:**
- 11-07 Beta (0101+1)
- 11-07 Experiment-A (0101+1)
- 11-07 Nightly-Control (0101+1)
- 11-14 Beta (0244+2)
- 11-14 Experiment-A (0244+2)
- 11-14 Experimental (0244+2)
- +5 more

**Possible assignees:** `@gmajoulet`

/cc @ampproject/release-on-duty

Start at extensions/amp-story/1.0/media-performance-metrics-service.js:413 and review the stack trace alongside src/event-helper-listen.js:58. Use the linked error report to understand when timeStamps is accessed on an undefined value, then verify the diagnosis against the referenced changes in #23962 and #12450; the issue is done when the reported error no longer occurs.

Written by the indexing model from the issue text.