Return a default user record if json is broken
Return a default user record if json is broken

It's possible that json_decode returns null. Mostly the json is broken.
AddMissingDefaultValues expects an array. Pass null will fail.

Signed-off-by: Daniel Kesselberg <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@danielkesselberg.de>

andreas-p/nextcloud-server,andreas-p/nextcloud-server,nextcloud/server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,nextcloud/server,andreas-p/nextcloud-server,nextcloud/server,nextcloud/server