[FIX] sign in and sign out were broken in rev 10019 as it doesn't provide a date to conversion of attendance time to employee timezone

lp bug: https://launchpad.net/bugs/1314589 fixed

bzr revid: yannick.vaucher@camptocamp.com-20140430113730-cn3xw66fbik8p32n

addons/hr_timesheet_sheet/hr_timesheet_sheet.py

@@ -407,6 +407,9 @@ class hr_attendance(osv.osv):
             employee = employee_obj.browse(cr, uid, employee_id, context=context)
             tz = employee.user_id.partner_id.tz
 
+        if not date:
+            date = time.strftime(DEFAULT_SERVER_DATETIME_FORMAT)
+
         att_tz = timezone(tz or 'utc')
 
         attendance_dt = datetime.strptime(date, DEFAULT_SERVER_DATETIME_FORMAT)