Update theme

Hi, i updated the Customizr theme version and got this comment:

Parse error: syntax error, unexpected ‘[‘ in /home/deb82584/domains/asandwhy.nl/public_html/wp-content/themes/customizr/core/class-fire-resources_scripts.php on line 504

The problem is I can’t get into my cms as on every page i try to enter the same message is shown.

How can i reset my webpage to the old customizr version, or how can i get the new customizr version to work as i can’t get into my cms.

The page I need help with: [log in to see the link]