coverity#1325053 Dereference after null check

pre-change !pSh logic inverted at

commit 1b15f486
Author: Miklos Vajna <vmiklos@collabora.co.uk>
Date:   Fri Feb 6 12:12:02 2015 +0100

    LOK: add LOK_CALLBACK_TEXT_SELECTION and implement it in sw

    Change-Id: I31662cb06add0d1a1c517b5f5416703aeaae1e77

Change-Id: If42741c4efce943aaff5081a1a75108470b2a488

sw/source/core/layout/trvlfrm.cxx

@@ -2018,7 +2018,7 @@ void SwRootFrm::CalcFrmRects(SwShellCrsr &rCrsr)
 
     SwViewShell *pSh = GetCurrShell();
 
-    bool bIgnoreVisArea = false;
+    bool bIgnoreVisArea = true;
     if (pSh)
         bIgnoreVisArea = pSh->GetViewOptions()->IsPDFExport() || pSh->isTiledRendering();