mshtml: Properly return NULL parentElement.

dlls/mshtml/htmlelem.c

@@ -848,6 +848,11 @@ static HRESULT WINAPI HTMLElement_get_parentElement(IHTMLElement *iface, IHTMLEl
     if(FAILED(hres))
         return hres;
 
+    if(!node) {
+        *p = NULL;
+        return S_OK;
+    }
+
     hres = IHTMLDOMNode_QueryInterface(node, &IID_IHTMLElement, (void**)p);
     IHTMLDOMNode_Release(node);
     if(FAILED(hres))

dlls/mshtml/tests/dom.c

@@ -5267,6 +5267,8 @@ static void test_insert_adjacent_elems(IHTMLDocument2 *doc, IHTMLElement *parent
     static const elem_type_t br_div_br[] = {ET_BR, ET_DIV, ET_BR};
 
     elem = test_create_elem(doc, "BR");
+    elem2 = test_elem_get_parent((IUnknown*)elem);
+    ok(!elem2, "get_parentElement returned %p\n", elem2);
     insert_adjacent_elem(parent, "BeforeEnd", elem);
     IHTMLElement_Release(elem);