PostgreSQL error (Segmentation Fault with message "SSL SYSCALL error: EOF detected")

Hello. I want to report error on PostgreSQL.

If I execute queries:

DROP TABLE IF EXISTS client_tt;
CREATE TABLE client_tt(id_client_tt integer NOT NULL, id_unique integer);
INSERT INTO client_tt(id_client_tt, id_unique) VALUES('1', '1');
ALTER TABLE ONLY client_tt ADD CONSTRAINT client_tt_pkey PRIMARY KEY (id_client_tt);
ALTER TABLE ONLY client_tt ADD CONSTRAINT client_tt_ibfk_7 FOREIGN KEY (id_unique) REFERENCES client_tt(id_client_tt) ON DELETE SET NULL DEFERRABLE;
ALTER TABLE client_tt ADD COLUMN tt_code_inn VARCHAR(12) NOT NULL DEFAULT '';
DELETE FROM client_tt;

Then system throws Segmentation Fault with message "SSL SYSCALL error: EOF detected".

Details:

PostgreSQL version:
postgres=# SELECT VERSION();
version
-----------------------------------------------------------------------------------------------------------
PostgreSQL 11.0 (Debian 11.0-1+b1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 8.2.0-9) 8.2.0, 64-bit
(1 row)

Linux version: Debian GNU/Linux testing (buster)
> cat /proc/version
Linux version 4.18.0-2-amd64 (debian-kernel(at)lists(dot)debian(dot)org) (gcc version 7.3.0 (Debian 7.3.0-30)) #1 SMP Debian 4.18.10-2 (2018-11-02)

psql version:
> PGPASSWORD=**** psql -h localhost -U postgres
psql (11.0 (Debian 11.0-1+b1))
SSL connection (protocol: TLSv1.3, cipher: TLS_AES_256_GCM_SHA384, bits: 256, compression: off)

The error is repeated if I run queries:
1) On this system by php7.2-pgsql
2) On Ubuntu 16.04.5 LTS by psql (11.0 (Ubuntu 11.0-1.pgdg16.04+2)) and by php7.2-pgsql

In /var/log/postgresql/postgresql-11-main.log I see:

2018-11-07 18:59:29.670 EET [12806] LOG: server process (PID 14341) was terminated by signal 11: Segmentation fault
2018-11-07 18:59:29.670 EET [12806] DETAIL: Failed process was running: DELETE FROM client_tt;
2018-11-07 18:59:29.686 EET [12806] LOG: terminating any other active server processes
2018-11-07 18:59:29.692 EET [12811] WARNING: terminating connection because of crash of another server process
2018-11-07 18:59:29.692 EET [12811] DETAIL: The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.
2018-11-07 18:59:29.692 EET [12811] HINT: In a moment you should be able to reconnect to the database and repeat your command.
2018-11-07 18:59:29.708 EET [16602] postgres(at)ddc_tests FATAL: the database system is in recovery mode