Cannot make it work in PHP 7.1

[robregonm]

First, thanks for an awesome extension.
Always get these warnings:

PHP message: PHP Warning:  reset() expects parameter 1 to be array, null given in /project/vendor/sweelix/yii2-sendgrid/src/Message.php on line 136 
PHP message: PHP Warning:  Variable passed to each() is not an array or object in /project/vendor/sweelix/yii2-sendgrid/src/Message.php on line 137
PHP message: PHP Warning:  reset() expects parameter 1 to be array, null given in /project/vendor/sweelix/yii2-sendgrid/src/Message.php on line 152 
PHP message: PHP Warning:  Variable passed to each() is not an array or object in /project/vendor/sweelix/yii2-sendgrid/src/Message.php on line 153

And silently fails.