Don't try to release the node if we haven't loaded one.

diff --git a/dlls/msxml3/domdoc.c b/dlls/msxml3/domdoc.c
index 3415fd8..2d83b7b 100644
--- a/dlls/msxml3/domdoc.c
+++ b/dlls/msxml3/domdoc.c
@@ -100,7 +100,8 @@
     ref = InterlockedDecrement( &This->ref );
     if ( ref == 0 )
     {
-        IXMLDOMElement_Release( This->node );
+        if ( This->node )
+            IXMLDOMElement_Release( This->node );
         HeapFree( GetProcessHeap(), 0, This );
     }