On theme settings you can upload 2 kinds of logo, one for white background and other for black. I changed them both, but on the footer nothing changed, it stays with the basel logo.
Footer logo doesn’t come from Theme Settings. It is simple widget area and you can place there anything: texts, images, widgets etc. At the moment there a simple text widget with logo image HTML tag. So you can change it in Appearance -> Widgets -> Footer Column 1.