engine: fix for GCC 7.x non-null check
engine: fix for GCC 7.x non-null check

Most likely the original author did too much copy & paste

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