[BUGFIX] Except when 'renderType' is not string in NodeFactory

In cases where `array_merge_recursive` is used to append
to a TCA configuration multiple times with the same
key, it will lead to transforming an array key with
a single value to an array of values instead.

The NodeFactory can not deal with this case.

This patch throws an exception in case no string
is found, and tries to hint at this possible
array scenario.

Resolves: #106177
Releases: main, 13.4, 12.4
Change-Id: I98ce2bafeabed23cfff6246f4f56918991366396
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/88261
Tested-by: core-ci <typo3@b13.com>
Tested-by: Garvin Hicking <gh@faktor-e.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Garvin Hicking <gh@faktor-e.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>

Author: garvinhicking

typo3/sysext/backend/Classes/Form/NodeFactory.php

@@ -159,6 +159,12 @@ public function create(array $data): NodeInterface
         }
         $type = $data['renderType'];
 
+        if (!is_string($type)) {
+            throw new Exception(
+                '"renderType" in TCA of field "[' . ($data['tableName'] ?? 'unknown') . '][' . ($data['fieldName'] ?? 'unknown') . ']" does not contain a string. It might be an array instead of a string which could be the result of an array_merge_recursive() operation, for example on existing "fieldControl" keys (these need to have unique array key indices).',
+                1739882175
+            );
+        }
         $className = $this->nodeTypes[$type] ?? $this->nodeTypes['unknown'];
 
         if (!empty($this->nodeResolver[$type])) {