Baloo doesn't remove the user.xdg.tags xattr when the tag is removed in Dolphin, instead leaving it empty.
Git commit f9b3e4f160e34ed675c370280c887cc4ef6c1331 by James D. Smith. Committed on 24/11/2017 at 22:27. Pushed by smithjd into branch 'master'. If the property value is null, remove the user.xdg.tag attribute. M +48 -8 src/usermetadata.cpp https://commits.kde.org/kfilemetadata/f9b3e4f160e34ed675c370280c887cc4ef6c1331