erp5_web_renderjs_ui: no need to workaround null values

jio 3.45.0 fixed the issue
6 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

00:52:33

passed ERP5.PerformanceTest-Master

00:26:02

failed ERP5.UnitTest-Master

01:14:16

failed ERP5.UnitTest-Master.Medusa

01:26:07

passed SlapOS.Eggs.UnitTest-Master.Python2

00:14:25

passed SlapOS.Eggs.UnitTest-Master.Python3

00:13:13