Throw DOM exception in insertAdjacentHTML if context becomes null

Source/core/html/HTMLElement.cpp

Index: Source/core/html/HTMLElement.cpp
diff --git a/Source/core/html/HTMLElement.cpp b/Source/core/html/HTMLElement.cpp
index c6115081340bd23f6d8d2fba5c9d51ffbf559a04..c9ca7578d6139d4713b362a2e3173ef70d5b5b25 100644
--- a/Source/core/html/HTMLElement.cpp
+++ b/Source/core/html/HTMLElement.cpp
@@ -506,12 +506,12 @@ Element* HTMLElement::insertAdjacentElement(const String& where, Element* newChi
     return toElement(returnValue);
 }
 
-// Step 3 of http://www.whatwg.org/specs/web-apps/current-work/multipage/apis-in-html-documents.html#insertadjacenthtml()
+// Step 1 of http://domparsing.spec.whatwg.org/#insertadjacenthtml()
 static Element* contextElementForInsertion(const String& where, Element* element, ExceptionState& exceptionState)
 {
     if (equalIgnoringCase(where, "beforeBegin") || equalIgnoringCase(where, "afterEnd")) {
         ContainerNode* parent = element->parentNode();
-        if (parent && !parent->isElementNode()) {
+        if (!parent || !parent->isElementNode()) {
             exceptionState.throwDOMException(NoModificationAllowedError, "The element has no parent.");
             return 0;
         }