中间表缺失表名

多对多关联的中间表，判断是否存在关联数据时报错：
SQLSTATE[42000]: Syntax error or access violation: 1103 Incorrect table name ''

<?php
namespace app\model;
use think\Model;
class Users extends Model
{
    //用户角色关联
    public function roles(): \think\model\relation\BelongsToMany
    {
        return $this->belongsToMany('Role','user_role','role_id','user_id');
    }
}


$user = User::find(1);  
$user->roles()->attached(2); //有数据存在时报错

报错信息内容

[10501]SQLSTATE[42000]: Syntax error or access violation: 1103 Incorrect table name ''
[/htdocs/api/vendor/topthink/think-orm/src/db/PDOConnection.php:867]
#0 /htdocs/api/vendor/topthink/think-orm/src/db/connector/Mysql.php(68): think\db\PDOConnection->getPDOStatement()
#1 /htdocs/api/vendor/topthink/think-orm/src/db/PDOConnection.php(444): think\db\connector\Mysql->getFields()
#2 /htdocs/api/vendor/topthink/think-orm/src/db/PDOConnection.php(401): think\db\PDOConnection->getTableFieldsInfo()
#3 /htdocs/api/vendor/topthink/think-orm/src/db/PDOConnection.php(363): think\db\PDOConnection->getCachedSchemaInfo()
#4 /htdocs/api/vendor/topthink/think-orm/src/db/PDOConnection.php(430): think\db\PDOConnection->getSchemaInfo()
#5 /htdocs/api/vendor/topthink/think-orm/src/db/PDOConnection.php(519): think\db\PDOConnection->getTableInfo()
#6 /htdocs/api/vendor/topthink/think-orm/src/db/concern/TableFieldInfo.php(60): think\db\PDOConnection->getFieldsType()
#7 /htdocs/api/vendor/topthink/think-orm/src/model/concern/DbConnect.php(87): think\db\Query->getFieldsType()
#8 /htdocs/api/vendor/topthink/think-orm/src/model/concern/Attribute.php(47): think\Model->getFields()
#9 /htdocs/api/vendor/topthink/think-orm/src/Model.php(150): think\Model->initializeData()
#10 /htdocs/api/vendor/topthink/think-orm/src/model/Pivot.php(49): think\Model->__construct()
#11 /htdocs/api/vendor/topthink/think-orm/src/Model.php(279): think\model\Pivot->__construct()
#12 /htdocs/api/vendor/topthink/think-orm/src/model/Pivot.php(75): think\Model->clone()
#13 /htdocs/api/vendor/topthink/think-orm/src/db/concern/ModelRelationQuery.php(673): think\model\Pivot->newInstance()
#14 /htdocs/api/vendor/topthink/think-orm/src/db/BaseQuery.php(1575): think\db\BaseQuery->resultToModel()
#15 /htdocs/api/vendor/topthink/think-orm/src/model/relation/BelongsToMany.php(613): think\db\BaseQuery->find()
#16 /htdocs/api/app/controller/User.php(203): think\model\relation\BelongsToMany->attached()
#17 [internal function]: app\controller\User->setUserRole()
#18 /htdocs/api/vendor/topthink/think-container/src/Container.php(349): ReflectionMethod->invokeArgs()
#19 /htdocs/api/vendor/topthink/framework/src/think/route/Dispatch.php(190): think\Container->invokeReflectMethod()
#20 /htdocs/api/vendor/topthink/framework/src/think/Pipeline.php(59): think\route\Dispatch->think\route\{closure}()
#21 /htdocs/api/vendor/topthink/framework/src/think/Pipeline.php(66): think\Pipeline->think\{closure}()
#22 /htdocs/api/vendor/topthink/framework/src/think/route/Dispatch.php(164): think\Pipeline->then()
#23 /htdocs/api/vendor/topthink/framework/src/think/route/dispatch/Controller.php(112): think\route\Dispatch->responseWithMiddlewarePipeline()
#24 /htdocs/api/vendor/topthink/framework/src/think/route/Dispatch.php(60): think\route\dispatch\Controller->exec()
#25 /htdocs/api/vendor/topthink/framework/src/think/Route.php(717): think\route\Dispatch->run()
#26 /htdocs/api/vendor/topthink/framework/src/think/Pipeline.php(59): think\Route->think\{closure}()
#27 /htdocs/api/vendor/topthink/framework/src/think/Pipeline.php(66): think\Pipeline->think\{closure}()
#28 /htdocs/api/vendor/topthink/framework/src/think/Route.php(716): think\Pipeline->then()
#29 /htdocs/api/vendor/topthink/framework/src/think/Http.php(208): think\Route->dispatch()
#30 /htdocs/api/vendor/topthink/framework/src/think/Http.php(198): think\Http->dispatchToRoute()
#31 /htdocs/api/vendor/topthink/framework/src/think/Pipeline.php(59): think\Http->think\{closure}()
#32 /htdocs/api/vendor/topthink/think-trace/src/TraceDebug.php(71): think\Pipeline->think\{closure}()
#33 [internal function]: think\trace\TraceDebug->handle()
#34 /htdocs/api/vendor/topthink/framework/src/think/Middleware.php(134): call_user_func()
#35 /htdocs/api/vendor/topthink/framework/src/think/Pipeline.php(85): think\Middleware->think\{closure}()
#36 /htdocs/api/vendor/topthink/framework/src/think/Pipeline.php(66): think\Pipeline->think\{closure}()
#37 /htdocs/api/vendor/topthink/framework/src/think/Http.php(197): think\Pipeline->then()
#38 /htdocs/api/vendor/topthink/framework/src/think/Http.php(162): think\Http->runWithRequest()
#39 /htdocs/api/vendor/topthink/think-swoole/src/concerns/InteractsWithHttp.php(148): think\Http->run()
#40 /htdocs/api/vendor/topthink/think-swoole/src/concerns/InteractsWithHttp.php(127): think\swoole\Manager->handleRequest()
#41 /htdocs/api/vendor/topthink/think-container/src/Container.php(299): think\swoole\Manager->think\swoole\concerns\{closure}()
#42 /htdocs/api/vendor/topthink/think-container/src/Container.php(363): think\Container->invokeFunction()
#43 /htdocs/api/vendor/topthink/think-swoole/src/Sandbox.php(81): think\Container->invoke()
#44 /htdocs/api/vendor/topthink/think-swoole/src/concerns/WithApplication.php(88): think\swoole\Sandbox->run()
#45 /htdocs/api/vendor/topthink/think-swoole/src/concerns/InteractsWithHttp.php(120): think\swoole\Manager->runInSandbox()
#46 [internal function]: think\swoole\Manager->think\swoole\concerns\{closure}()
#47 {main}

Start in src/model/relation/BelongsToMany.php around attached(), then follow the pivot creation through src/model/Pivot.php and the schema lookup in src/db/PDOConnection.php. Reproduce the provided relation with MySQL and attached(2); done means it no longer queries an empty table name and correctly reports the association.