coverity#736861 Dereference before null check

Change-Id: I4930657852f0ee4c3d7a751b9c90a2a65d329c40

sw/source/core/uibase/app/docsh.cxx

@@ -818,7 +818,7 @@ void SwDocShell::Draw( OutputDevice* pDev, const JobSetup& rSetup,
     pDev->SetFillColor();
     pDev->SetLineColor();
     pDev->SetBackground();
-    bool bWeb = 0 != PTR_CAST(SwWebDocShell, this);
+    const bool bWeb = this->ISA(SwWebDocShell);
     SwPrintData aOpts;
     SwViewShell::PrtOle2( pDoc, SW_MOD()->GetUsrPref(bWeb), aOpts, pDev, aRect );
     pDev->Pop();