From ee888875bb01031c6f21e48832313641ee6d726e Mon Sep 17 00:00:00 2001
From: Max Kunzelmann <maxdev@posteo.de>
Date: Sun, 20 Mar 2022 00:38:07 +0100
Subject: [PATCH] Fixes the undefined index error with the DAV property
 getlastmodified

Signed-off-by: Max Kunzelmann <maxdev@posteo.de>
---
 lib/private/Files/Storage/DAV.php | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/private/Files/Storage/DAV.php b/lib/private/Files/Storage/DAV.php
index b4a85755b20..e4cea9dd60b 100644
--- a/lib/private/Files/Storage/DAV.php
+++ b/lib/private/Files/Storage/DAV.php
@@ -587,7 +587,7 @@ class DAV extends Common {
 				return false;
 			}
 			return [
-				'mtime' => strtotime($response['{DAV:}getlastmodified']),
+				'mtime' => isset($response['{DAV:getlastmodified']) ? strtotime($response['{DAV:}getlastmodified']) : false,
 				'size' => (int)isset($response['{DAV:}getcontentlength']) ? $response['{DAV:}getcontentlength'] : 0,
 			];
 		} catch (\Exception $e) {
@@ -804,9 +804,12 @@ class DAV extends Common {
 				} else {
 					return false;
 				}
-			} else {
+			} elseif (isset($response['{DAV:}getlastmodified'])) {
 				$remoteMtime = strtotime($response['{DAV:}getlastmodified']);
 				return $remoteMtime > $time;
+			} else {
+				// neither `getetag` nor `getlastmodified` is set
+				return false;
 			}
 		} catch (ClientHttpException $e) {
 			if ($e->getHttpStatus() === 405) {