-Werror=nonnull-compare

...where "this" must be (derived from) View, in View::InsertData.

Before 89d39bc1 "tdf#94559: 4th step to remove
rtti.hxx," that was

  ISA( View )

which had originally been introduced as

  ISA( SdView )

into SdView::InsertData with 82453a8c "#80266#:
added D&D functionality for slide view" in 2001 (and then, both in concert,
SdView::InsertData changed to View::InsertData and the ISA( SdView ) changed to
ISA( View ) with ee8db8ad "INTEGRATION: CWS
impress1: #111996# Transition to stacked sub-shells. Introduction of namespace
sd."

So just assume it was always only a harmless glitch that is good to go.

Change-Id: I5a99e401feb2a4c4455469b58c803ccab06694f5

sd/source/ui/view/sdview3.cxx

@@ -359,7 +359,7 @@ bool View::InsertData( const TransferableDataHelper& rDataHelper,
     {
         const View* pSourceView = pOwnData->GetView();
 
-        if( pOwnData->GetDocShell() && pOwnData->IsPageTransferable() && dynamic_cast< View *>( this) !=  nullptr )
+        if( pOwnData->GetDocShell() && pOwnData->IsPageTransferable() )
         {
             mpClipboard->HandlePageDrop (*pOwnData);
             bReturn = true;