Fixed Incorrect arguments to mysqld_stmt_execute

This error appears to only happen on CI and not locally, despite
everything running with the same version. I have no idea why this is the
case.

Since I removed the `nil` from the prepared statement, it is possible
that this problem is related to the issues linked below, but I'm not sure. I also
don't really know how to debug in github actions yet, so I don't know
how to confirm if this is indeed the case.

- go-sql-driver/mysql#209
- launchbadge/sqlx#125
- https://stackoverflow.com/questions/16726752/sending-null-in-a-prepared-statement-for-mysql-doesnt-seem-to-work?rq=1

Author: shuhaowu

test/helpers/db_helper.rb

@@ -125,13 +125,13 @@ def seed_random_data(connection, database_name: DEFAULT_DB, table_name: DEFAULT_
     return if number_of_rows == 0
 
     transaction(connection) do
-      sqlargs = (["(?,?)"]*number_of_rows).join(", ")
-      sql = "INSERT INTO #{dbtable} (id, data) VALUES #{sqlargs}"
+      sqlargs = (["(?)"]*number_of_rows).join(", ")
+      sql = "INSERT INTO #{dbtable} (data) VALUES #{sqlargs}"
       insert_statement = connection.prepare(sql)
 
       rand_rows = []
       number_of_rows.times do
-        rand_rows += [nil, rand_data]
+        rand_rows += [rand_data]
       end
 
       insert_statement.execute(*rand_rows)