Make the space optional after a comma separator (Webklex#437)

Author: marc0adam

src/Header.php

@@ -510,7 +510,7 @@ private function decodeAddresses($values): array {
         }
 
         foreach ($values as $address) {
-            foreach (preg_split('/, (?=(?:[^"]*"[^"]*")*[^"]*$)/', $address) as $split_address) {
+            foreach (preg_split('/, ?(?=(?:[^"]*"[^"]*")*[^"]*$)/', $address) as $split_address) {
                 $split_address = trim(rtrim($split_address));
 
                 if (strpos($split_address, ",") == strlen($split_address) - 1) {