tdf#118316: fix off-by-1 error (outline level is 0-based)

regression since commit 4730b23b

Change-Id: I50627cde3a9a91189db61e19850768412b058064
Reviewed-on: https://gerrit.libreoffice.org/56295
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

sw/source/ui/frmdlg/cption.cxx

@@ -376,7 +376,7 @@ void SwCaptionDialog::DrawSample()
             if( pFieldType && pFieldType->GetOutlineLvl() < MAXLEVEL )
             {
                 SwNumberTree::tNumberVector aNumVector;
-                aNumVector.insert(aNumVector.end(), pFieldType->GetOutlineLvl(), 1);
+                aNumVector.insert(aNumVector.end(), pFieldType->GetOutlineLvl() + 1, 1);
 
                 OUString sNumber( rSh.GetOutlineNumRule()->
                                 MakeNumString(aNumVector, false ));