If you're finding by id, then yes, you should be handling exceptions.
If you're not finding by id, then if nothing's there, you should
handle that eventuality accordingly.
So say the docs:
* Find by id: This can either be a specific id (1), a list of ids
(1, 5, 6), or an array of ids ([5, 6, 10]). If no record can be found
for all of the listed ids, then RecordNotFound will be raised.
* Find first: This will return the first record matched by the
options used. These options can either be specific conditions or
merely an order. If no record can matched, nil is returned.
* Find all: This will return all the records matched by the
options used. If no records are found, an empty array is returned.