Server closed the connection unexpectedly

My fuzzer finds a bug in Postgres, which makes the connection closed
unexpectedly.

--- Steps to reproduce the bug ---
1. /usr/local/pgsql/bin/psql -d postgres -c "drop database redb";
2. /usr/local/pgsql/bin/psql -d postgres -c "create database redb";
3. /usr/local/pgsql/bin/psql -d redb -f pg_testdb10_bk.sql;
4. /usr/local/pgsql/bin/psql -d redb -f unexpected.sql

pg_testdb10_bk.sql and unexpected.sql are attached.

--- Expected behavior ---
No error triggered.

--- Actual behavior ---
The test case makes the connection closed unexpectedly:

psql:unexpected.sql:39: server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
psql:unexpected.sql:39: error: connection to server was lost

--- Postgres version ---
Github commit: 3f1aaaa180689f2015e7f7bd01c9be6d7a993b42
Version: PostgreSQL 16beta1 on x86_64-pc-linux-gnu, compiled by gcc 
(Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0, 64-bit

--- Platform information ---
Platform: Ubuntu 20.04
Kernel: Linux 5.4.0-147-generic