project: fix a NameError in TALES

This happens in project related task report dialog (
testProjectRelatedTaskReport from
erp5_report_renderjs_ui_test:testFunctionalRJSReportLanguage )
6 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

01:01:14

passed ERP5.PerformanceTest-Master

00:26:36

failed ERP5.UnitTest-Master

01:42:25

failed ERP5.UnitTest-Master.Medusa

01:52:12

passed SlapOS.Eggs.UnitTest-Master.Python2

00:23:21

passed SlapOS.Eggs.UnitTest-Master.Python3

00:14:22