[22967] Bug #589865 In the report "Budget flow" period it doesn't work ok

change the report head line to show the period date for (- period 1).
Author : Carsten Rinke <carsten.rinke@gmx.de>

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/branches/2.4@22974 57a11ea4-9604-0410-9ed3-97b8803252fd

src/report/standard-reports/budget-flow.scm

@@ -311,7 +311,7 @@
         (gnc:html-document-set-title!
           doc (sprintf #f (_ "%s: %s - %s")
             report-name (gnc-budget-get-name budget)
-            (gnc-print-date (gnc-budget-get-period-start-date budget period))))
+            (gnc-print-date (gnc-budget-get-period-start-date budget (- period 1)))))
 
         ;; Display accounts and totals
         (set! accounts-totals (gnc:html-table-add-budget-types! html-table split-up-accounts budget period exchange-fn report-currency))