https://github.com/wikimedia/mediawiki-extensions-Popups/blob/master/src/changeListeners/eventLogging.js#L71
For example, with the pageLoaded event. Probably with others.
Guard the token deduplication logic with the token existence.
Reported originally here T167273#3364463 :
>>! In T167273#3364463, @pmiazga wrote:
> @phuedx - there is one tiny issue with tracking PageLoaded events.
>
> We create a `pageLoaded` event here - https://github.com/wikimedia/mediawiki-extensions-Popups/blob/master/src/reducers/eventLogging.js#L170 - event doesn't contain `linkInteractionToken` property.
>
> Then in https://github.com/wikimedia/mediawiki-extensions-Popups/blob/master/src/changeListeners/eventLogging.js#L71 we read `linkInteractionToken` which is undefined.
>
> It would be nice to fix it so our code is consistent.