Error message: Undefined array key "width" in Header

I have installed the STREAM theme but keep getting the below two error messages:
Undefined array key "width" in
/homepages/10/d832457524/htdocs/clickandbuilds/DigitalAssetsPrime/wp-content/themes/generatepress/inc/structure/header.php

Undefined array key "height" in
/homepages/10/d832457524/htdocs/clickandbuilds/DigitalAssetsPrime/wp-content/themes/generatepress/inc/structure/header.php

How do I fix this?

I havent made any changes to the theme, nor uploaded any plugins.. I have deleted the theme and opened again.. the error message is still there..

Any help would be appreciated

THanks