On wmf.19 (not in wmf.18) and in betalabs, RecentChanges and Watchlist produce the following console error upon loading
Uncaught TypeError: Cannot read property 'toggle' of undefined at MwRcfiltersUiFilterTagMultiselectWidget.FilterTagMultiselectWidget.onChangeTags at MwRcfiltersUiFilterTagMultiselectWidget.OO.EventEmitter.emit at MwRcfiltersUiFilterTagMultiselectWidget.OO.ui.mixin.GroupElement.clearItems
With the specific reference to this.emptyFilterMessage.toggle(this.isEmpty());
FilterTagMultiselectWidget.prototype.onChangeTags = function() { if (this.controller.isInitialized()) { FilterTagMultiselectWidget.parent.prototype.onChangeTags.call(this); } this.emptyFilterMessage.toggle(this.isEmpty()); }