From a26c24928e795b7eaa7a6d201bc6a76895fe5bca Mon Sep 17 00:00:00 2001
From: Xun Gong <hyouuu@gmail.com>
Date: Mon, 24 May 2021 00:53:26 -0700
Subject: [PATCH] fix optional

---
 lib/src/models/documents/nodes/node.dart | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/src/models/documents/nodes/node.dart b/lib/src/models/documents/nodes/node.dart
index 6bb0fb97..08335727 100644
--- a/lib/src/models/documents/nodes/node.dart
+++ b/lib/src/models/documents/nodes/node.dart
@@ -53,6 +53,9 @@ abstract class Node extends LinkedListEntry<Node> {
 
   /// Offset in characters of this node in the document.
   int get documentOffset {
+    if (parent == null) {
+      return offset;
+    }
     final parentOffset = (parent is! Root) ? parent!.documentOffset : 0;
     return parentOffset + offset;
   }