Fatal Error w/plugin Causing entire site to crash

I’ve just discovered I cannot view my site or sign in to it using /wp-login/ or /wp-admin/
all attempts just display the same error message:

Fatal error: Can’t use function return value in write context in /var/www/vhosts/apera.nz/httpdocs/wp-content/plugins/ultimate-social-media-plus/ultimate_social_media_icons.php on line 669

If I could sign in I’m sure I could sort it out but I can’t seem to do that.

Any ideas please?

Thanks

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