CRM-20892 Fix issue where saving to the database wasn't creating a ne…

…w modified_date

CRM/Mailing/BAO/Mailing.php

@@ -1600,11 +1600,19 @@ public static function add(&$params, $ids = array()) {
     ) {
       $params['replyto_email'] = $params['from_email'];
     }
-
     $mailing->copyValues($params);
 
+    // CRM-20892 Unset Modifed Date here so that MySQL can correctly set an updated modfied date.
+    unset($mailing->modified_date);
     $result = $mailing->save();
 
+    // CRM-20892 Re find record after saing so we can set the updated modified date in the result.
+    $mailing->find(TRUE);
+
+    if (isset($mailing->modified_date)) {
+      $result->modified_date = $mailing->modified_date;
+    }
+
     if (!empty($ids['mailing'])) {
       CRM_Utils_Hook::post('edit', 'Mailing', $mailing->id, $mailing);
     }