TypeError: undefined is not an object (evaluating 'mw.popups.experiment.isUserInCondition')

I've seen this a few times on my local machine but have no idea under what circumstances it occurs.

Looking at the code I see that if the ext.popups.core module is loaded before mw.popups.experiment it could cause the above error which might break the feature and interfere with event logging as the property popupEnabled uses mw.popups.getEnabledState() which uses isUserInCondition. If this required value was undefined this would lead to dropped events.
(cc @Tbayer )