Yii2 后台登陆页面显示空白 [ 2.0 版本 ]

后台login 控制器：

<?php

namespace app\modules\admin\controllers;

use yii\web\Controller;
use app\models\LoginForm;

class LoginController extends Controller {

	public function actionIndex() {
		$model = new LoginForm();

		$this->render('index', ['model'=>$model]);
	}
}

view 模块：

<?php
use yii\helpers\Html;
use yii\bootstrap\ActiveForm;

/* @var $this yii\web\View */
/* @var $form yii\bootstrap\ActiveForm */
/* @var $model app\models\LoginForm */

$this->title = 'Login';
$this->params['breadcrumbs'][] = $this->title;
?>
<div class="site-login">
    <h1><?= Html::encode($this->title) ?></h1>

    <p>Please fill out the following fields to login:</p>

    <?php $form = ActiveForm::begin([
        'id' => 'login-form',
        'options' => ['class' => 'form-horizontal'],
        'fieldConfig' => [
            'template' => "{label}\n<div class=\"col-lg-3\">{input}</div>\n<div class=\"col-lg-8\">{error}</div>",
            'labelOptions' => ['class' => 'col-lg-1 control-label'],
        ],
    ]); ?>

    <?= $form->field($model, 'username') ?>

    <?= $form->field($model, 'password')->passwordInput() ?>

    <?= $form->field($model, 'rememberMe', [
        'template' => "<div class=\"col-lg-offset-1 col-lg-3\">{input}</div>\n<div class=\"col-lg-8\">{error}</div>",
    ])->checkbox() ?>

    <div class="form-group">
        <div class="col-lg-offset-1 col-lg-11">
            <?= Html::submitButton('Login', ['class' => 'btn btn-primary', 'name' => 'login-button']) ?>
        </div>
    </div>

    <?php ActiveForm::end(); ?>
</div>

访问http://localhost/basic/web/index.php?r=admin/login/index， 页面显示空白，
log里最后一message为：

3	16:11:28.730	info	yii\web\Session::open	Session started
E:\phpEnv\yii2\basic\views\layouts\main.php (41)
E:\phpEnv\yii2\basic\modules\admin\controllers\LoginController.php (13)