Crash when calling getCueAsHTML() on a TextTrackCue with empty text

Source/core/html/track/WebVTTParser.cpp

Index: Source/core/html/track/WebVTTParser.cpp
diff --git a/Source/core/html/track/WebVTTParser.cpp b/Source/core/html/track/WebVTTParser.cpp
index 4a7b524f5922c12f1894f8bc1d2e4719f9ec68e1..4b2dfc22fc6148a2aba985b4302aba35f032b9a3 100644
--- a/Source/core/html/track/WebVTTParser.cpp
+++ b/Source/core/html/track/WebVTTParser.cpp
@@ -328,13 +328,16 @@ PassRefPtr<DocumentFragment>  WebVTTParser::createDocumentFragmentFromCueText(co
     // 4.8.10.13.4 WebVTT cue text parsing rules and
     // 4.8.10.13.5 WebVTT cue text DOM construction rules.
 
-    if (!text.length())
-        return 0;
-
     ASSERT(m_scriptExecutionContext->isDocument());
     Document* document = toDocument(m_scriptExecutionContext);
 
     RefPtr<DocumentFragment> fragment = DocumentFragment::create(document);
+
+    if (!text.length()) {
+        fragment->parserAppendChild(Text::create(document, ""));
+        return fragment;
+    }
+
     m_currentNode = fragment;
     m_tokenizer->reset();
     m_token.clear();