PHP errors

Having our error logs filled up with the same error.

[Mon Apr 25 18:15:08.597170 2016] [:error] [pid 13477] [client 184.2.177.153:65431] PHP Warning: Illegal string offset ‘additional_javascript_selectors’ in /nas/content/live/dramystore/wp-content/plugins/woocommerce-improved-external-products/wc-improved-external-products.php on line 121, referer: http://www.amymyersmd.com/

Running on WP Engine with Cloudflare. Can you address?

https://ww.wp.xz.cn/plugins/woocommerce-improved-external-products/