From 1079c3759134ae70049253e8f64737beca65956f Mon Sep 17 00:00:00 2001
From: Julia Lange <julia.warnke@visuellverstehen.de>
Date: Thu, 23 Nov 2023 11:57:31 +0100
Subject: [PATCH] fix: prevent call to undefined text property

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

diff --git a/src/Nodes/Heading.php b/src/Nodes/Heading.php
index 01fd732..a2878cd 100644
--- a/src/Nodes/Heading.php
+++ b/src/Nodes/Heading.php
@@ -18,7 +18,10 @@ public function renderHTML($node, $HTMLAttributes = [])
 
         // Add slugified id to specific headlines.
         if (in_array($node->attrs->level, config('anchor-navigation.heading.levels', []))) {
-            $HTMLAttributes['id'] = Str::slug($node->content[0]->text);
+
+            if (property_exists($node->content[0], 'text') && !is_null($node->content[0]->text)) {
+                $HTMLAttributes['id'] = Str::slug($node->content[0]->text);
+            }
         }
 
         return [