From 4ddc299e5bd5383da8a0dd653a38ccad832a150b Mon Sep 17 00:00:00 2001
From: Meritoo <github@meritoo.pl>
Date: Thu, 20 Jun 2019 21:04:44 +0200
Subject: [PATCH] Fix "Cannot call method add on possibly null value" bug
 pointed by Psalm

---
 src/Utilities/Date.php | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/Utilities/Date.php b/src/Utilities/Date.php
index 30ff7d1..421b411 100644
--- a/src/Utilities/Date.php
+++ b/src/Utilities/Date.php
@@ -120,7 +120,10 @@ class Date
 
                 if (null !== $lastMonth) {
                     $dateStart = $lastMonth->getEndDate();
-                    $dateStart->add(new DateInterval('P1D'));
+
+                    if (null !== $dateStart) {
+                        $dateStart->add(new DateInterval('P1D'));
+                    }
                 }
 
                 if (null !== $nextMonth) {