erp5_core: do not check acquired checkbox if nothing is acquired

6 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

01:40:11

failed ERP5.PerformanceTest-Master

00:25:55

failed ERP5.UnitTest-Master

01:59:31

failed ERP5.UnitTest-Master.Medusa

01:44:26

passed SlapOS.Eggs.UnitTest-Master.Python2

00:12:53

passed SlapOS.Eggs.UnitTest-Master.Python3

00:14:20