simplify SwClientIter dtor

Change-Id: Ibf41f0c53b0454029601dd1cac479bdd82f50f0c

sw/source/core/attr/calbck.cxx

@@ -377,8 +377,7 @@ SwClientIter::SwClientIter( const SwModify& rModify )
 
 SwClientIter::~SwClientIter()
 {
-    if( pClientIters )
-    {
+    assert(pClientIters);
     // reorganize list of ClientIters
     if( pClientIters == this )
         pClientIters = pNxtIter;
@@ -386,14 +385,12 @@ SwClientIter::~SwClientIter()
     {
         SwClientIter* pTmp = pClientIters;
         while( pTmp->pNxtIter != this )
-                if( nullptr == ( pTmp = pTmp->pNxtIter ) )
         {
-                    OSL_ENSURE( this, "Lost my pointer" );
-                    return ;
+            assert(pTmp);
+            pTmp = pTmp->pNxtIter;
         }
         pTmp->pNxtIter = pNxtIter;
     }
-    }
 }
 
 SwClient* SwClientIter::operator++()