Use indexed getToken()

Change-Id: I28d1a4f5a32bbe6e2278e9694c85d9a72dde8a23
Reviewed-on: https://gerrit.libreoffice.org/67650
Tested-by: Jenkins
Reviewed-by: Matteo Casalin <matteo.casalin@yahoo.com>

sd/source/ui/docshell/docshel2.cxx

@@ -318,7 +318,8 @@ bool DrawDocShell::IsNewPageNameValid( OUString & rInOutPageName, bool bResetStr
     if (rInOutPageName.startsWith(aStrPage) &&
         rInOutPageName.getLength() > aStrPage.getLength())
     {
-        OUString sRemainder = rInOutPageName.getToken(1, ' ');
+        sal_Int32 nIdx{ aStrPage.getLength() };
+        OUString sRemainder = rInOutPageName.getToken(0, ' ', nIdx);
         if (sRemainder[0] >= '0' && sRemainder[0] <= '9')
         {
             // check for arabic numbering