add customfield delete function

zimbraSingle.php

@@ -97,6 +97,9 @@ function zimbraSingleCreateCustomFields($packageconfigoption)
 {
     $whmcs = App::self();
     $productID = $whmcs->get_req_var('id');
+    Capsule::table('tblcustomfields')
+        ->where('relid', '=', $productID)
+        ->delete();
     try {
         Capsule::table('tblcustomfields')
         ->insert(