Fix regression importing navigation portlet (ConstraintNotSatisfied, Error Value: /)
Fix regression importing navigation portlet (ConstraintNotSatisfied, Error Value: /)

https://dev.plone.org/ticket/10232

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