Website down after update Kalium

I updated to the new Kalium via Wordpress and now I see the following on my homepage:
Fatal error: Call to undefined function imagescale() in /home2/enjojoto/public_html/wp-content/themes/kalium/inc/lib/class-dominantcolors.php on line 197

At first I thought it had to do with the image size of the pictures in revolution slider. But even when I disable revolution slider it doesn’t change. I am not sure what I should adjust.

Hey there. You can get support for Kalium by @Laborator on their Support Page. These are just the general forums. Cheers!