I could confirm the issue on my test site that if no logo is set then the default theme logo is displayed instead of removing logo therefore notified the theme developer about this so that it will be fixed.

The issue will be fixed ASAP.

In the meanwhile you can try removing the logo by adding the following CSS code in the Custom CSS code option of your theme on the below path.

Admin Area -> Appearance -> Theme Settings -> Custom Code -> CSS Code

.header-logo {
    display: none;
}