Issue with featured image on “Testimonial” page

Hi! We just discovered if we set the 'Featured Image' on the "Testimonials" Essential Content Types plugin setting, the image doesn't appear. Here's a link that demonstrates this: https://www.birthandbeauty.com/testimonial/ You'll notice the single color background in the header instead of the selected image. I looked at the underlying CSS and found this gets generated:

.wrapper::before {
    background-image: url( );
    background-position: center top;
    background-repeat: no-repeat;
    background-size: cover;
}

Notice the background-image property has an empty "url" attribute. This works just fine on the "Portfolio" page (setting the image in the Portfolio Essential Content Types Plugin section). Please report this to the developers so it can be fixed. Thanks in advance!