Segfault with NULL value in cell

• asyncpg version: 0.23.0
• PostgreSQL version: 13
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?: No
• Python version: 3.8
• Platform: Ubuntu Xenial
• Did you install asyncpg with pip?: Yes
• Can the issue be reproduced under both asyncio and
  uvloop?: Yes

My table looks like this, and is using the citext extension

CREATE TABLE public.items
(
    item_id     bigint                       NOT NULL,
    tags        citext[] default '{}' not null
);

I have a simple query

query = """SELECT tags FROM items WHERE item_id = 304028"""

async with pool.acquire() as c:
    result = await c.fetchval(query)
    print(result)
    val = result[2]

This gives the following output
['debuff', 'buff', <NULL>]
And upon trying to access the second item of the list results a segmentation fault occurs.

Inspecting the database with PyCharm's database tab shows this cell as having the value {debuff,buff,""}

Es werden keine Quelldateien oder Tests genannt. Beginne damit, die gemeldete asyncpg 0.23.0-Abfrage gegen das bereitgestellte PostgreSQL-Schema zu reproduzieren und zu untersuchen, wie das citext[]-Ergebnis mit einem NULL-Element decodiert wird; fertig ist es, wenn derselbe Zugriff keinen Segmentation Fault mehr verursacht und der NULL-Wert sicher behandelt wird.