S3 table function path matching: single value in curly brackets does not work

[ray-at-github]

Describe the issue
S3 table function path matching with curly brackets {}, when there are multiple values it works like a charm. However it returns no rows when there is only 1 value within the curly brackets. It would be ideal if it also supports a single value (or even an empty list), because sometimes the list of values is constructed from an array programmatically.

How to reproduce
21.6.4.26

Multiple values works:

SELECT count(*)
FROM s3('https://storage.yandexcloud.net/my-test-bucket-768/{some,another}_prefix/some_file_1.csv', 'CSV', 'name String, value UInt32')

Query id: 8363ef9d-c6af-4036-9f63-2da969df5732

┌─count()─┐
│       6 │
└─────────┘

1 rows in set. Elapsed: 2.632 sec.

Single value doesn't:

SELECT count(*)
FROM s3('https://storage.yandexcloud.net/my-test-bucket-768/{some}_prefix/some_file_1.csv', 'CSV', 'name String, value UInt32')

Query id: 79ec92e1-a13e-4164-a999-08334c40a3fe

┌─count()─┐
│       0 │
└─────────┘

1 rows in set. Elapsed: 1.353 sec.

Expected behavior
Ideally it also supports single value