Remove the concept of document.documentElement

sky/engine/core/editing/SpellChecker.cpp

Index: sky/engine/core/editing/SpellChecker.cpp
diff --git a/sky/engine/core/editing/SpellChecker.cpp b/sky/engine/core/editing/SpellChecker.cpp
index 6d01adbaa44a50b8afda8d8938ecb308c642f1ea..f3496631e7eb6e3efc5bce90b8c3376f6f1fd4d2 100644
--- a/sky/engine/core/editing/SpellChecker.cpp
+++ b/sky/engine/core/editing/SpellChecker.cpp
@@ -163,7 +163,7 @@ void SpellChecker::advanceToNextMisspelling(bool startBeforeSelection)
         // when spell checking the whole document before sending the message.
         // In that case the document might not be editable, but there are editable pockets that need to be spell checked.
 
-        position = firstEditableVisiblePositionAfterPositionInRoot(position, m_frame.document()->documentElement()).deepEquivalent();
+        position = firstEditableVisiblePositionAfterPositionInRoot(position, m_frame.document()).deepEquivalent();
         if (position.isNull())
             return;