bika_listing: Fix categorized display when items have no category
bika_listing: Fix categorized display when items have no category

DeBortoliWines/Bika-LIMS,labsanmartin/Bika-LIMS,veroc/Bika-LIMS,anneline/Bika-LIMS,labsanmartin/Bika-LIMS,veroc/Bika-LIMS,anneline/Bika-LIMS,DeBortoliWines/Bika-LIMS,labsanmartin/Bika-LIMS,anneline/Bika-LIMS,veroc/Bika-LIMS,rockfruit/bika.lims,DeBortoliWines/Bika-LIMS,rockfruit/bika.lims