plugins/ArtNet: fix Qt4 build
plugins/ArtNet: fix Qt4 build

kripton/qlcplus,plugz/qlcplus,mcallegari/qlcplus,nedmech/qlcplus,plugz/qlcplus,sbenejam/qlcplus,kripton/qlcplus,sbenejam/qlcplus,plugz/qlcplus,mcallegari/qlcplus,nedmech/qlcplus,plugz/qlcplus,sbenejam/qlcplus,sbenejam/qlcplus,nedmech/qlcplus,kripton/qlcplus,mcallegari/qlcplus,sbenejam/qlcplus,plugz/qlcplus,mcallegari/qlcplus,nedmech/qlcplus,mcallegari/qlcplus,kripton/qlcplus,kripton/qlcplus,plugz/qlcplus,mcallegari/qlcplus,sbenejam/qlcplus,mcallegari/qlcplus,kripton/qlcplus,plugz/qlcplus,nedmech/qlcplus,sbenejam/qlcplus,kripton/qlcplus,nedmech/qlcplus