sw: fix assert in SwViewShell::FillPrtDoc()

The point node isn't necessarily the start node; this will assert in
SwTextFrame::MapModelToView: Assertion `SwFrame::GetDep() == pNode' failed
when selecting a table and then File->Print->Print Selection.

Thanks Samuel for the hint.

(regression from 067a53bb)

Change-Id: I7f58b79e068e8b7817261e81f999721ebfcfdcf1
Reviewed-on: https://gerrit.libreoffice.org/65421
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>

sw/source/core/view/vprint.cxx

@@ -358,7 +358,8 @@ void SwViewShell::FillPrtDoc( SwDoc *pPrtDoc, const SfxPrinter* pPrt)
     {
         SwShellTableCursor* pShellTableCursor = pFESh->GetTableCursor();
 
-        const SwContentNode* pContentNode = pShellTableCursor->GetNode().GetContentNode();
+        const SwContentNode *const pContentNode =
+            pShellTableCursor->Start()->nNode.GetNode().GetContentNode();
         const SwContentFrame *const pContentFrame = pContentNode ? pContentNode->getLayoutFrame(GetLayout(), pShellTableCursor->Start()) : nullptr;
         if( pContentFrame )
         {