[Enhancement] Prevent empty string values from getOrderProperty func return value

[rizdaprasetya]

SNAP-Woocommerce/class/class.midtrans-utils.php

Lines 35 to 42 in c1be238

	public static function getOrderProperty($order, $property){
	$functionName = "get_".$property;
	if (method_exists($order, $functionName)){ // WC v3
	return (string)$order->{$functionName}();
	} else { // WC v2
	return (string)$order->{$property};
	}
	}

This function should

• check if the return value is empty string "", then do not return empty string. Because it may cause issue if billing_email is empty string, Snap API will reject w/ msg "customer_details.email format is invalid"

Enhancement needed to prevent that issue.

Reporting merchant: G019146562 NextCool