Null check split node parent in outdentParagraph

https://bugs.webkit.org/show_bug.cgi?id=240806

Patch by Rob Buis <rbuis@igalia.com> on 2022-05-23
Reviewed by Wenson Hsieh.

The split node parent needs an extra null check to access its parent
before safely calling hasEditableStyle.

* Source/WebCore/editing/IndentOutdentCommand.cpp:
(WebCore::IndentOutdentCommand::outdentParagraph):

Canonical link: https://commits.webkit.org/250895@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@294691 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WebCore/editing/IndentOutdentCommand.cpp

@@ -164,6 +164,7 @@ void IndentOutdentCommand::outdentParagraph()
             if (ContainerNode* splitPointParent = splitPoint->parentNode()) {
                 if (splitPointParent->hasTagName(blockquoteTag)
                     && !splitPoint->hasTagName(blockquoteTag)
+                    && splitPointParent->parentNode()
                     && splitPointParent->parentNode()->hasEditableStyle()) // We can't outdent if there is no place to go!
                     splitElement(downcast<Element>(*splitPointParent), *splitPoint);
             }