Tokens in captions appear unsubstituted if the token's value is empty

I've made a photo gallery using Views, where each photo is a node. I want my images' captions to come from one of the nodes' optional fields. But if the field is empty on a node, I get the token in plain text as the caption, instead of simply getting no caption.

I've attached a screenshot as an example. The caption works perfectly whenever the field is there, but does this whenever it's absent.