Use getXWeak in xmlhelp

Change-Id: Iaea6bf7c539d1ab5e0399e07531be08f2764f488
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/150887
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

xmlhelp/source/treeview/tvfactory.cxx

@@ -84,7 +84,7 @@ TVFactory::createInstanceWithArguments(
 {
     if( ! m_xHDS.is() )
     {
-        m_xHDS = static_cast<cppu::OWeakObject*>(new TVChildTarget( m_xContext ));
+        m_xHDS = cppu::getXWeak(new TVChildTarget( m_xContext ));
     }
 
     OUString hierview;