where clause going through a OneToOne and ManyToMany fails without using $in

[merceyz]

Describe the bug

Running a find operation in which the where clause goes through a OneToOne and a ManyToMany without using the $in operator causes an exception

Stack trace

DriverException: Cannot read property '0' of undefined
    at SqliteExceptionConverter.convertException (C:\repro\.yarn\$$virtual\@mikro-orm-core-virtual-8a09e8cc28\0\cache\@mikro-orm-core-npm-4.0.5-89140dbf7c-747675fcd5.zip\node_modules\@mikro-orm\core\platforms\ExceptionConverter.js:8:16)
    at SqliteExceptionConverter.convertException (C:\repro\.yarn\$$virtual\@mikro-orm-sqlite-virtual-cf327cb9f8\0\cache\@mikro-orm-sqlite-npm-4.0.5-b162945642-e2ba86a3e8.zip\node_modules\@mikro-orm\sqlite\SqliteExceptionConverter.js:46:22)
    at SqliteDriver.convertException (C:\repro\.yarn\$$virtual\@mikro-orm-core-virtual-8a09e8cc28\0\cache\@mikro-orm-core-npm-4.0.5-89140dbf7c-747675fcd5.zip\node_modules\@mikro-orm\core\drivers\DatabaseDriver.js:168:54)
    at C:\repro\.yarn\$$virtual\@mikro-orm-core-virtual-8a09e8cc28\0\cache\@mikro-orm-core-npm-4.0.5-89140dbf7c-747675fcd5.zip\node_modules\@mikro-orm\core\drivers\DatabaseDriver.js:172:24
    at SqliteDriver.find (C:\repro\.yarn\$$virtual\@mikro-orm-knex-virtual-9185994f82\0\cache\@mikro-orm-knex-npm-4.0.5-75b85d5235-c870f5de55.zip\node_modules\@mikro-orm\knex\AbstractSqlDriver.js:42:24)
    at SqliteDriver.findOne (C:\repro\.yarn\$$virtual\@mikro-orm-knex-virtual-9185994f82\0\cache\@mikro-orm-knex-npm-4.0.5-75b85d5235-c870f5de55.zip\node_modules\@mikro-orm\knex\AbstractSqlDriver.js:56:21)
    at SqlEntityManager.findOne (C:\repro\.yarn\$$virtual\@mikro-orm-core-virtual-8a09e8cc28\0\cache\@mikro-orm-core-npm-4.0.5-89140dbf7c-747675fcd5.zip\node_modules\@mikro-orm\core\EntityManager.js:162:22)
    at C:\repro\index.ts:32:2

previous TypeError: Cannot read property '0' of undefined
    at QueryBuilderHelper.fieldName (C:\repro\.yarn\$$virtual\@mikro-orm-knex-virtual-9185994f82\0\cache\@mikro-orm-knex-npm-4.0.5-75b85d5235-c870f5de55.zip\node_modules\@mikro-orm\knex\query\QueryBuilderHelper.js:398:38)
    at QueryBuilderHelper.prefix (C:\repro\.yarn\$$virtual\@mikro-orm-knex-virtual-9185994f82\0\cache\@mikro-orm-knex-npm-4.0.5-75b85d5235-c870f5de55.zip\node_modules\@mikro-orm\knex\query\QueryBuilderHelper.js:375:31)
    at QueryBuilderHelper.mapper (C:\repro\.yarn\$$virtual\@mikro-orm-knex-virtual-9185994f82\0\cache\@mikro-orm-knex-npm-4.0.5-75b85d5235-c870f5de55.zip\node_modules\@mikro-orm\knex\query\QueryBuilderHelper.js:28:24)
    at QueryBuilderHelper.appendQuerySubCondition (C:\repro\.yarn\$$virtual\@mikro-orm-knex-virtual-9185994f82\0\cache\@mikro-orm-knex-npm-4.0.5-75b85d5235-c870f5de55.zip\node_modules\@mikro-orm\knex\query\QueryBuilderHelper.js:215:20)
    at C:\repro\.yarn\$$virtual\@mikro-orm-knex-virtual-9185994f82\0\cache\@mikro-orm-knex-npm-4.0.5-75b85d5235-c870f5de55.zip\node_modules\@mikro-orm\knex\query\QueryBuilderHelper.js:197:18
    at Array.forEach (<anonymous>)
    at QueryBuilderHelper.appendQueryCondition (C:\repro\.yarn\$$virtual\@mikro-orm-knex-virtual-9185994f82\0\cache\@mikro-orm-knex-npm-4.0.5-75b85d5235-c870f5de55.zip\node_modules\@mikro-orm\knex\query\QueryBuilderHelper.js:186:27)
    at C:\repro\.yarn\$$virtual\@mikro-orm-knex-virtual-9185994f82\0\cache\@mikro-orm-knex-npm-4.0.5-75b85d5235-c870f5de55.zip\node_modules\@mikro-orm\knex\query\QueryBuilder.js:176:54
    at Function.runIfNotEmpty (C:\repro\.yarn\$$virtual\@mikro-orm-core-virtual-8a09e8cc28\0\cache\@mikro-orm-core-npm-4.0.5-89140dbf7c-747675fcd5.zip\node_modules\@mikro-orm\core\utils\Utils.js:394:13)
    at QueryBuilder.getKnexQuery (C:\repro\.yarn\$$virtual\@mikro-orm-knex-virtual-9185994f82\0\cache\@mikro-orm-knex-npm-4.0.5-75b85d5235-c870f5de55.zip\node_modules\@mikro-orm\knex\query\QueryBuilder.js:176:22)

To Reproduce

// User.ts
import { Entity, PrimaryKey, OneToOne, ManyToMany, Collection } from '@mikro-orm/core';
import { Group } from './Group';
import { Profile } from './Profile';

@Entity()
export class User {
	@PrimaryKey()
	id: number;

	@OneToOne(() => Profile)
	profile: Profile;

	@ManyToMany(() => Group, (group) => group.users)
	groups = new Collection<Group>(this);
}

// Profile.ts
import { Entity, PrimaryKey, OneToOne } from '@mikro-orm/core';
import { User } from './User';

@Entity()
export class Profile {
	@PrimaryKey()
	id: number;

	@OneToOne(() => User, (user) => user.profile)
	user: User;
}

// Group.ts
import { Entity, PrimaryKey, ManyToMany, Collection } from '@mikro-orm/core';
import { User } from './User';

@Entity()
export class Group {
	@PrimaryKey()
	id: number;

	@ManyToMany(() => User, (user) => user.groups, { owner: true })
	users = new Collection<User>(this);
}

// index.ts
import { MikroORM } from '@mikro-orm/core';
import { Group } from './Group';
import { Profile } from './Profile';
import { User } from './User';

(async () => {
	const orm = await MikroORM.init({
		type: 'sqlite',
		dbName: ':memory:',
		debug: true,
		entities: [User, Profile, Group],
	});

	await orm.getSchemaGenerator().ensureDatabase();
	await orm.getSchemaGenerator().createSchema();

	const user = new User();
	user.id = 123;
	user.profile = new Profile();
	user.profile.id = 456;

	const group = new Group();
	group.id = 789;
	group.users.add(user);

	await orm.em.persist(user).flush();
	orm.em.clear();

	// OK
	await orm.em.getRepository(Profile).findOne({ user: { groups: { $in: [789] } } });
	// Error
	await orm.em.getRepository(Profile).findOne({ user: { groups: [789] } });

	await orm.close(true);
})();

Expected behavior
Query should succeed both with and without using the $in operator

Versions

Dependency	Version
node	12.18.3
typescript	4.0.2
@mikro-orm/core	4.0.5
@mikro-orm/mysql	4.0.5
@mikro-orm/sqlite	4.0.5