This is a known core issue, see e.g. this ticket. There is work done fixing this issue by a complete rewrite of the importer, but no ETA for it yet.
For now as this is only a Notice you can safely ignore it for the time being.
This is a known core issue, see e.g. this ticket. There is work done fixing this issue by a complete rewrite of the importer, but no ETA for it yet.
For now as this is only a Notice you can safely ignore it for the time being.