Hi, I was facing some issue with my theme and initially I thought it might be my theme issue. The support for the theme got back to me:
If you de-activate marketpress plugin it looks normally?
Because if i de-activate the rule that plugin loads the line disappears
Here it's with that activated
So you can contact the plugin author to inform it about this.
Meanwhile you can add this CSS to wp-admin -> theme options -> general settings -> quick css
display: initial !important;
Something to look into?