give better hints for the whodunnit in SwClient/Modify

Change-Id: Ic30f70cae1258fcf9e703d85093d52a059c9cd53

sw/source/core/attr/calbck.cxx

@@ -152,8 +152,7 @@ void SwModify::Add( SwClient* pDepend )
         {
             for(auto& rIter : sw::ClientIteratorBase::our_pClientIters->GetRingContainer())
             {
-                OSL_ENSURE( &rIter.m_rRoot != m_pWriterListeners, "Client added to active ClientIter" );
-                //assert(&rIter.m_rRoot != m_pWriterListeners);
+                SAL_WARN_IF(&rIter.m_rRoot == m_pWriterListeners, "sw.core", "a " << typeid(*pDepend).name() << " client added as listener to a " << typeid(*this).name() << " during client iteration.");
             }
         }
 #endif