Error: Cannot read property 'obj' of undefined

[dreamofabear]

Started seeing these in 1908150025400. A top 10 error report in the first day of 1%.

Error: Cannot read property 'obj' of undefined
at obj (https://raw.githubusercontent.com/ampproject/amphtml/1908150025400/src/service.js:395)
at getServiceInternal (https://raw.githubusercontent.com/ampproject/amphtml/1908150025400/src/service.js:196)
at (https://raw.githubusercontent.com/ampproject/amphtml/1908150025400/src/services.js:280)
at Services$$module$src$services.extensionsFor (https://raw.githubusercontent.com/ampproject/amphtml/1908150025400/src/service/crypto-impl.js:155)
at loadPolyfill_ (https://raw.githubusercontent.com/ampproject/amphtml/1908150025400/src/service/crypto-impl.js:81)
at sha384 (https://raw.githubusercontent.com/ampproject/amphtml/1908150025400/src/service/crypto-impl.js:123)
at sha384Base64 (https://raw.githubusercontent.com/ampproject/amphtml/1908150025400/src/service/cid-impl.js:655)
at getRandomString64 (https://raw.githubusercontent.com/ampproject/amphtml/1908150025400/src/service/document-info-impl.js:95)
at get (https://raw.githubusercontent.com/ampproject/amphtml/1908150025400/src/services.js:269)
at Services$$module$src$services.documentInfoForDoc (https://raw.githubusercontent.com/ampproject/amphtml/1908150025400/src/service/resources-impl.js:1223)

Stack trace implies that "extensions" service is not registered on the given window, which is confusing.

UA appears to be always "Miui Browser".