lone·ly /ˈloʊnli/
–adjective, -li·er, -li·est.
1. affected with, characterized by, or causing a depressing feeling of being alone; lonesome.
2. destitute of sympathetic or friendly companionship, intercourse, support, etc.: a lonely exile.
3. lone; solitary; without company; companionless.
4. remote from places of human habitation; desolate; unfrequented; bleak: a lonely road.
5. standing apart; isolated: a lonely tower.
Just because it is an empty space does not mean it is lonely. Loneliness is an emotion, and shadows have none.