From 8101b0e8fa4c45fc0f7e02e46cf1d0c0ade17e16 Mon Sep 17 00:00:00 2001
From: Tim Nagel <tim@nagel.com.au>
Date: Tue, 13 Mar 2018 10:27:08 +1100
Subject: [PATCH] Return null for empty IntervalSpec

---
 Date/IntervalFormatter.php | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Date/IntervalFormatter.php b/Date/IntervalFormatter.php
index 1ff451b..2df2a1a 100644
--- a/Date/IntervalFormatter.php
+++ b/Date/IntervalFormatter.php
@@ -50,6 +50,10 @@ public static function formatDateInterval(\DateInterval $interval)
                 $spec .= $interval->s . 'S';
             }
         }
+        
+        if ($spec === 'P') {
+            return null;
+        }
 
         return $spec;
     }