--- a/editor/libeditor/HTMLEditRules.cpp
+++ b/editor/libeditor/HTMLEditRules.cpp
@@ -2177,16 +2177,17 @@ HTMLEditRules::SplitMailCites(bool* aHan
   // that the serializer will insert a break where the user saw one.
   // FYI: splitCiteNodeResult grabs the previous node with nsCOMPtr.  So, it's
   //      safe to access previousNodeOfSplitPoint even after changing the DOM
   //      tree and/or selection even though it's raw pointer.
   nsIContent* previousNodeOfSplitPoint =
     splitCiteNodeResult.GetPreviousNode();
   if (previousNodeOfSplitPoint &&
       previousNodeOfSplitPoint->IsHTMLElement(nsGkAtoms::span) &&
+      previousNodeOfSplitPoint->GetPrimaryFrame() &&
       previousNodeOfSplitPoint->GetPrimaryFrame()->
                                   IsFrameOfType(nsIFrame::eBlockFrame)) {
     nsCOMPtr<nsINode> lastChild =
       previousNodeOfSplitPoint->GetLastChild();
     if (lastChild && !lastChild->IsHTMLElement(nsGkAtoms::br)) {
       // We ignore the result here.
       EditorRawDOMPoint endOfPreviousNodeOfSplitPoint;
       endOfPreviousNodeOfSplitPoint.SetToEndOf(previousNodeOfSplitPoint);