handle non existing owners when handling dav requests
handle non existing owners when handling dav requests

Signed-off-by: Robin Appelman <474ee9ee179b0ecf0bc27408079a0b15eda4c99d@icewind.nl>

nextcloud/server,michaelletzgus/nextcloud-server,Ardinis/server,nextcloud/server,pixelipo/server,endsguy/server,nextcloud/server,Ardinis/server,xx621998xx/server,whitekiba/server,endsguy/server,pixelipo/server,whitekiba/server,Ardinis/server,michaelletzgus/nextcloud-server,whitekiba/server,Ardinis/server,andreas-p/nextcloud-server,xx621998xx/server,whitekiba/server,Ardinis/server,pixelipo/server,endsguy/server,nextcloud/server,xx621998xx/server,xx621998xx/server,endsguy/server,michaelletzgus/nextcloud-server,endsguy/server,whitekiba/server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,pixelipo/server,pixelipo/server,xx621998xx/server,andreas-p/nextcloud-server,michaelletzgus/nextcloud-server,andreas-p/nextcloud-server