This fix was not complete. It seems that images are added as an object, and then array_map fails.
I have correct this line to the following:
ppom-addon-cart-edit.php lines 309 and 443
replace:
$query_args[$key] = is_array($value) ? array_map( 'urlencode', $value ) : urlencode($value);
with
$query_args[$key] = ( is_array($value) ) ? $this->my_array_map('urlencode',$value) : urlencode($value);
And added function to ppom-addon-cart-edit.php:
function my_array_map($function, $arrar) {
$result = array();
foreach ($arrar as $key => $val) {
$val = (is_object($val)) ? (array)$val : $val;
$result[$key] = (is_array($val) ? $this->my_array_map($function, $val) : $function($val));
}
return $result;
}