Ensure cached value of ContentNodeSlim/popular is never None (#5486)
Ensure cached value of ContentNodeSlim/popular is never None (#5486)

Ensure cached value of ContentNodeSlim/popular is never None
lyw07/kolibri,lyw07/kolibri,learningequality/kolibri,indirectlylit/kolibri,lyw07/kolibri,learningequality/kolibri,indirectlylit/kolibri,learningequality/kolibri,mrpau/kolibri,mrpau/kolibri,mrpau/kolibri,indirectlylit/kolibri,lyw07/kolibri,learningequality/kolibri,indirectlylit/kolibri,mrpau/kolibri