@tomaszsita, I think this will help:
I found the problem. It is when the admin area is SSL.
In the cropImage() function in lib/ManualImageCrop.php:
$uploadsDir[‘baseurl’] is changed to https via the preg_replace, but wp_get_attachment_image_src returns http, not https for the $src_file_url and $dst_file_url. So the str_replace functions on lines 165 and 171 are not working, and thus not returning file paths as expected.
There is probably a more elegant way to do this but, I added the following lines as a temporary fix:
On line 163:
if (is_ssl()) {
$src_file_url = preg_replace('#^https://#i', 'https://', $src_file_url);
}
On line 171:
if (is_ssl()) {
$dst_file_url = preg_replace('#^https://#i', 'https://', $dst_file_url);
}