I have started getting this error on my woocommerce checkout page:
Strict Standards: Only variables should be passed by reference in /home/c/chimimuru/chimiwoo/public_html/wp-content/plugins/woocommerce/includes/class-wc-countries.php on line 967
I believe that this has happened after theme update, although not 100% sure.
I have version 10.5
Here is a screenshot: