base: fix error printing deliveries with only \n in description

Default printout (used for order, packing lists, invoices etc) was raising
error for deliveries with cells when the resource descrption was only \n
8 jobs for arnau in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

02:58:40

failed ERP5.PerformanceTest-Master

00:34:37

failed ERP5.UnitTest-Master

02:48:34

failed ERP5.UnitTest-Master.Medusa

04:11:14

passed SlapOS.Eggs.UnitTest-Master.Python2

00:31:19

passed SlapOS.Eggs.UnitTest-Master.Python3

00:43:58

passed SlapOS.Eggs.UnitTest-Master.Python2

00:25:48

passed SlapOS.Eggs.UnitTest-Master.Python3

00:11:40