msxml3: Handle NULL child in appendChild().

dlls/msxml3/node.c

@@ -625,6 +625,9 @@ HRESULT node_append_child(xmlnode *This, IXMLDOMNode *child, IXMLDOMNode **outCh
     VARIANT var;
     HRESULT hr;
 
+    if (!child)
+        return E_INVALIDARG;
+
     hr = IXMLDOMNode_get_nodeType(child, &type);
     if(FAILED(hr) || type == NODE_ATTRIBUTE) {
         if (outChild) *outChild = NULL;

dlls/msxml3/tests/domdoc.c

@@ -8878,6 +8878,12 @@ static void test_appendChild(void)
     EXPECT_NO_CHILDREN(doc);
     EXPECT_NO_CHILDREN(doc2);
 
+    hr = IXMLDOMDocument_appendChild(doc2, NULL, NULL);
+    ok(hr == E_INVALIDARG, "got 0x%08x\n", hr);
+
+    hr = IXMLDOMElement_appendChild(elem, NULL, NULL);
+    ok(hr == E_INVALIDARG, "got 0x%08x\n", hr);
+
     /* append from another document */
     hr = IXMLDOMDocument_appendChild(doc2, (IXMLDOMNode*)elem, NULL);
     ok(hr == S_OK, "got 0x%08x\n", hr);