Default image retrieved is NOT the thumbnail

Using latest version of the plugin (1.0.1), I took the opportunity of this recent release to update my theme code and remove some deprecated arguments.

However, if I’m not adding 'size' => 'thumbnail' to the argument list, I do NOT retrieve the thumbnail ; however the documentation explains it should be the default.

Did I understand incorrectly something, or is there a bug here?

My code sample (with the ‘size’ argument, so that it works):

<?php if (function_exists('get_the_image')) { echo get_the_image(array ('size' => 'thumbnail', 'link_to_post' => false, 'width' => '120', 'height' => '120', 'default_image' => get_bloginfo('stylesheet_directory').'/library/images/PointingHand.png')); } ?>

Thanks in advance for your support.

https://www.ads-software.com/plugins/get-the-image/