We have a pair of nodes internally at the moment at @Vernalis which will convert missingcells in collection columns to empty collections, and empty collections to missing cells. Tbh, I thought we had released them to the community already, but it looks like we haven’t. Let me know if you would like me to get them on our release list!
They are on our trunk (nightly) build now, under Community Nodes -> Vernalis -> Collections, along with a 3rd new node, ‘Collection Size’:
One slight caveat is that I have a problem uploading test cases to the build server this evening, so the new nodes are technically untested - I will put an announcement out on the Vernalis forum page when that is resolved, but they should work OK! (I just installed them on my PC at home and they work fine)