fix: warn user when no dense points are generated
fix: warn user when no dense points are generated

mapillary/OpenSfM,oscarlorentzon/OpenSfM,oscarlorentzon/OpenSfM,oscarlorentzon/OpenSfM,mapillary/OpenSfM,oscarlorentzon/OpenSfM,mapillary/OpenSfM,oscarlorentzon/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM