--- a/editor/libeditor/HTMLEditRules.cpp
+++ b/editor/libeditor/HTMLEditRules.cpp
@@ -3729,16 +3729,19 @@ HTMLEditRules::WillMakeList(Selection* a
     if (!curList) {
       SplitNodeResult splitCurNodeResult =
         MaybeSplitAncestorsForInsert(listType, atCurNode);
       if (NS_WARN_IF(splitCurNodeResult.Failed())) {
         return splitCurNodeResult.Rv();
       }
       curList =
         htmlEditor->CreateNode(listType, splitCurNodeResult.SplitPoint());
+      if (NS_WARN_IF(!curList)) {
+        return NS_ERROR_FAILURE;
+      }
       // remember our new block for postprocessing
       mNewBlock = curList;
       // curList is now the correct thing to put curNode in
       prevListItem = nullptr;
 
       // atCurNode is now referring the right node with mOffset but
       // referring the left node with mRef.  So, invalidate it now.
       atCurNode.Clear();