[IMP] improve code

bzr revid: fka@tinyerp.com-20130618084755-977k4ulv5c1bbcrk

addons/account/account_cash_statement.py

@@ -158,16 +158,17 @@ class account_cash_statement(osv.osv):
                 limit=1,
                 context=context
         )
-        
+
         opening_details_ids = self._get_cash_open_box_lines(cr, uid, journal_id, context)
         if opening_details_ids:
             result['value']['opening_details_ids'] = opening_details_ids
 
-        if statement_ids:
+        if not statement_ids:
             return result
 
         st = self.browse(cr, uid, statement_ids[0], context=context)
         result.setdefault('value', {}).update({'last_closing_balance' : st.balance_end_real})
+
         return result
 
     _columns = {