Trigger generating ERROR 2006 (HY000), connection time outs - database

Question

I currently am trying to integrate a trigger into my sql code.
However, I am facing an issue where integrating the trigger
yields connection issues and breaks any future queries while
using that sourced database. I am using MariaDB.
This is what I have.
/* TRIGGERS */
DELIMITER |
CREATE TRIGGER max_trials
BEFORE INSERT ON Customer_Trials
FOR EACH ROW
BEGIN
DECLARE dummy INT DEFAULT 0;
IF NOT (SELECT customer_id
FROM Active_Customers
WHERE NEW.customer_id = customer_id)
THEN
SET #dummy = 1;
END IF;
END |
DELIMITER ;
I source a file which contains all of this code.
When trigger uncommented and I source (the table will not exist),
I get this output
MariaDB [(none)]> SOURCE db.sql;
Query OK, 0 rows affected, **1 warning** (0.000 sec)
Query OK, 1 row affected (0.000 sec)
Database changed
Query OK, 0 rows affected (0.028 sec)
Query OK, 0 rows affected (0.019 sec)
...
...
**ERROR 2013 (HY000) at line 182 in file: 'db.sql': Lost connection to MySQL server during query**
Notice that a warning is produced at the top
and an error is produced at the bottom. Now let's look at the
warning:
MariaDB [carpets]> SHOW WARNINGS;
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (111)
ERROR: Can't connect to the server
In the above snippets, you see a warning and an error, but
referring to the issue of a loss of connection, for some
reason that I do not understand.
Let's look at the other case.
When I drop the database and reload with trigger commented out,
I recieve the following result:
MariaDB [(none)]> SOURCE carpet.sql;
Query OK, 9 rows affected (0.042 sec)
Query OK, 1 row affected (0.000 sec)
Database changed
Query OK, 0 rows affected (0.018 sec)
...
...
Query OK, 0 rows affected (0.003 sec)
I do not receive any issues. From this, it appears that the
trigger is causing an issue which prevents defined functionality.
I cannot insert or do much after I have generated the error, for every
query after will result in a connection error.
Having just got my hands on triggers, would anyone happen to have
an idea of what is going on here?