Marina Abramovic is one of the most powerful artists of our time. Her medium is performance, the human body as a maker and object of art. In the arresting and illuminating documentary “Marina Abramovic: The Artist is Present,” about her landmark 2012 exhibition at New York’s Museum of Modern Art — entitled “The Artist is Present” — we’re treated to cinematic validation of magic, of the sublime enveloping the banal. Much of the footage involves Abramovic and a parade of museum-goers simply looking at each other in silence. The intense fullness of “nothing” has never been more obvious. Or beautiful. See the film and see how you feel.