From 45e8e9c42065202b54368bde0809c453bd661c46 Mon Sep 17 00:00:00 2001
From: Vladimir Falcon <v.falcon@familie-redlich.de>
Date: Tue, 23 Mar 2021 13:10:47 +0100
Subject: [PATCH] [BUGFIX] Avoid call to implode function with an invalid
 argument.

The given argument $parameterArray['itemFormElValue'] is not always an
array resulting in PHP warning.
---
 .../backend/Classes/Form/Element/SelectTreeElement.php    | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/typo3/sysext/backend/Classes/Form/Element/SelectTreeElement.php b/typo3/sysext/backend/Classes/Form/Element/SelectTreeElement.php
index d54e78ed8f..a636fbc838 100644
--- a/typo3/sysext/backend/Classes/Form/Element/SelectTreeElement.php
+++ b/typo3/sysext/backend/Classes/Form/Element/SelectTreeElement.php
@@ -165,7 +165,13 @@ class SelectTreeElement extends AbstractFormElement
         $html[] =                       ' data-tree-show-toolbar="' . $showHeader . '"';
         $html[] =                       ' name="' . htmlspecialchars($parameterArray['itemFormElName']) . '"';
         $html[] =                       ' id="treeinput' . $formElementId . '"';
-        $html[] =                       ' value="' . htmlspecialchars(implode(',', $parameterArray['itemFormElValue'])) . '"';
+
+        if(is_array($parameterArray['itemFormElValue'])) {
+            $html[] =                   ' value="' . htmlspecialchars(implode(',', $parameterArray['itemFormElValue'])) . '"';
+        }else {
+            $html[] =                   ' value="' . htmlspecialchars($parameterArray['itemFormElValue']) . '"';
+        }
+
         $html[] =                   '/>';
         $html[] =               '</div>';
         $html[] =               '<div id="' . $treeWrapperId . '" class="svg-tree-wrapper" style="height: ' . $heightInPx . 'px;"></div>';
-- 
2.27.0