SwPagePreView: initialize sPageStr

this adds "Page " to the page number info in the statusbar and to the
scrollbar's tooltip in the page preview mode.

Change-Id: Ia1dda0e98777465ef87364f12437449ca7787510

sw/source/ui/uiview/pview.cxx

@@ -1189,6 +1189,7 @@ SwPagePreView::SwPagePreView(SfxViewFrame *pViewFrame, SfxViewShell* pOldSh):
     SfxViewShell( pViewFrame, SWVIEWFLAGS ),
     aViewWin( &pViewFrame->GetWindow(), *this ),
     nNewPage(USHRT_MAX),
+    sPageStr(SW_RES(STR_PAGE)),
     pHScrollbar(0),
     pVScrollbar(0),
     pPageUpBtn(0),