PHP 7.2 Warning in addons.api.php

I got this warning after upgrading to PHP 7.2:

PHP Warning: count(): Parameter must be an array or an object that implements Countable in /wp-content/plugins/iwp-client/addons.api.php

Plugin Version: 1.6.8.1

See also:
https://wiki.php.net/rfc/counting_non_countables

Fix (backwards compatible):

diff -ur iwp-client-23/addons.api.php iwp-client-24/addons.api.php
--- iwp-client-23/addons.api.php	2017-12-15 10:54:51.532245753 +0100
+++ iwp-client-24/addons.api.php	2017-12-15 11:08:06.676780082 +0100
@@ -37,7 +37,7 @@
 	function iwp_mmb_function_exists($callback)
 	{
 		global $iwp_core;
-		if (count($callback) === 2) {
+		if (is_array($callback) && count($callback) === 2) {
 			if (!method_exists($callback[0], $callback[1]))
 				wp_die($iwp_core->iwp_dashboard_widget('Information', '', '<p>Class ' . get_class($callback[0]) . ' does not contain <b>"' . $callback[1] . '"</b> function</p>', '', '50%'));
 		} else {