There is a small empty box (class="galleria-infolayer") shown on each photo regardless of the overlay settings and contents of title, description etc. fields. It is enough that the 'Show Overlay' option is set to anything else than 'Never'.
I want to display captions only in one of my galleries, therefore I'd expect the plugin not to show the box unless there is something to display inside it - e.g. the 'Show Description' option is ON and the description is not empty.
That would be the expected behavior anyway, wouldn't it? :)