coverity#1438212 Unchecked dynamic_cast

Change-Id: I9c346fd09603d086542f7f3cb355c7e5acc3378e
Reviewed-on: https://gerrit.libreoffice.org/58609
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

sw/source/core/unocore/unotbl.cxx

@@ -4040,12 +4040,12 @@ void SwXTableRows::removeByIndex(sal_Int32 nIndex, sal_Int32 nCount)
     pUnoCursor->SetMark();
     pUnoCursor->GetPoint()->nNode = *pBLBox->GetSttNd();
     pUnoCursor->Move(fnMoveForward, GoInNode);
-    SwUnoTableCursor* pCursor = dynamic_cast<SwUnoTableCursor*>(pUnoCursor.get());
+    SwUnoTableCursor& rCursor = dynamic_cast<SwUnoTableCursor&>(*pUnoCursor.get());
     {
         // HACK: remove pending actions for selecting old style tables
-        UnoActionRemoveContext aRemoveContext(*pCursor);
+        UnoActionRemoveContext aRemoveContext(rCursor);
     }
-    pCursor->MakeBoxSels();
+    rCursor.MakeBoxSels();
     {   // these braces are important
         UnoActionContext aAction(pFrameFormat->GetDoc());
         pFrameFormat->GetDoc()->DeleteRow(*pUnoCursor);