The tag is present in Lintian version 2.104.328. That is the most recent version we know about.
Using dpatch requires you to explicitly list all patches you want to apply in debian/patches/00list. This package build-depends on dpatch, but does not provide a patch list. You should either remove the dpatch build dependency or add a patch list.
Note that an empty file cannot be represented in the Debian diff, so an empty patch list will disappear in the source package. If you intended for the series file to be empty, add a comment line.