One of the DateTimes doesn't represent the date of the friendship, but
when the friend has updated their Mii.
I noticed this when playing with the friend servers researching
information about the data stored on the FRD sysmodule.
The friendship date is still stored internally, but it's not provided to
the user anymore.
Now database getters do error handling aswell, and in case of any error,
the NEX or GRPC method throws a proper error about it.
There are still some doubts on how to handle errors when a list of data
is processed, so for now skip that element on the list and continue.
Also add some constant errors to do better error handling.
Now that we can return errors to nex-protocols-go and it will handle it,
we can improve how errors are being handled in friends.
There's probably room for improvement from this, since I haven't added
error handling on some database getters due to uncertainties on whether
the error should interrupt an action or not.
