From dae51e28a1bcfc57dc8a723e08f5af7c6917b923 Mon Sep 17 00:00:00 2001
From: Aleksander Machniak <machniak@kolabsys.com>
Date: Thu, 13 Jul 2023 12:27:07 +0200
Subject: [PATCH] Fix PHP8 warning

---
 plugins/libcalendaring/libcalendaring.php | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/plugins/libcalendaring/libcalendaring.php b/plugins/libcalendaring/libcalendaring.php
index e2de7f2f..a87461e6 100644
--- a/plugins/libcalendaring/libcalendaring.php
+++ b/plugins/libcalendaring/libcalendaring.php
@@ -1545,6 +1545,10 @@ class libcalendaring extends rcube_plugin
      */
     public static function to_php_date_format($from)
     {
+        if (!is_string($from)) {
+            return '';
+        }
+
         // "dd.MM.yyyy HH:mm:ss" => "d.m.Y H:i:s"
         return strtr(strtr($from, array(
             'YYYY' => 'Y',
@@ -1581,6 +1585,10 @@ class libcalendaring extends rcube_plugin
      */
     public static function from_php_date_format($from)
     {
+        if (!is_string($from)) {
+            return '';
+        }
+
         // "d.m.Y H:i:s" => "dd.MM.yyyy HH:mm:ss"
         return strtr($from, array(
             'y' => 'YY',