Mobile Version – line across logo

The site we are building with Unicon has a problem when moving to a mobile size version. A line appears across the logo, please see screen shots. We are using the central logo header (Header 4).

http://www.pixhoster.info/f/2016-11/61787d5a04988b745bb18b1d310e5e2d.png

Please can you advise if this is a bug and whether there is a way to stop this happening?

Many thanks

Ticket