Added code to convert null tag/category lists to #f -- however, possibly
this should be handled in Civet, by treating null lists as false.
Revert "Added code to convert null tag/category lists to #f -- however, possibly"

This reverts commit fbe58541fbeec1188edc2b8b007e9cf6b3b22cbb.
Fixed bug where null lists for categories/tags were causing an error.