[Editing] Make InsertListCommand check endingSelection() editability.

Source/core/editing/InsertListCommand.cpp

Index: Source/core/editing/InsertListCommand.cpp
diff --git a/Source/core/editing/InsertListCommand.cpp b/Source/core/editing/InsertListCommand.cpp
index 9ad50f6c0fa3954af9f4c7b3d439715462dd97c6..c69d02ec9a8339d97bb4278dd3be230881867462 100644
--- a/Source/core/editing/InsertListCommand.cpp
+++ b/Source/core/editing/InsertListCommand.cpp
@@ -172,7 +172,7 @@ void InsertListCommand::doApply()
                     // If endOfSelection is null, then some contents have been deleted from the document.
                     // This should never happen and if it did, exit early immediately because we've lost the loop invariant.
                     ASSERT(endOfSelection.isNotNull());
-                    if (endOfSelection.isNull())
+                    if (endOfSelection.isNull() || !endOfSelection.rootEditableElement())
                         return;
                     startOfLastParagraph = startOfParagraph(endOfSelection, CanSkipOverEditingBoundary);
                 }