Small error in log - version 2.0.0-beta.1

[marc-farre]

With version 2.0.0-beta.1, I often get:

Error: Call to a member function __toString() on null in
/usr/www/humhub/protected/modules/linkpreview/controllers/IndexController.php:73
Stack trace:
#0
/usr/www/humhub/protected/modules/linkpreview/controllers/IndexController.php(48):
humhub\modules\linkpreview\controllers\IndexController->parseMetaImage()
#1 [internal function]:
humhub\modules\linkpreview\controllers\IndexController->actionFetch()
#2
/usr/www/humhub/protected/vendor/yiisoft/yii2/base/InlineAction.php(57):
call_user_func_array()
#3
/usr/www/humhub/protected/vendor/yiisoft/yii2/base/Controller.php(178):
yii\base\InlineAction->runWithParams()
#4
/usr/www/humhub/protected/vendor/yiisoft/yii2/base/Module.php(552):
yii\base\Controller->runAction()
#5
/usr/www/humhub/protected/vendor/yiisoft/yii2/web/Application.php(103):
yii\base\Module->runAction()
#6
/usr/www/humhub/protected/vendor/yiisoft/yii2/base/Application.php(384):
yii\web\Application->handleRequest()
#7
/usr/www/humhub/index.php(25):
yii\base\Application->run()
#8 {main}

The bug is here:

$imageUrls = $info->getMetas()->get('og:image:url') ?: $info->getMetas()->get('og:image') ?: [$info->image->__toString()];

As $info->image can be null.

[marc-farre]

@gevorgmansuryan I have the bug also line 56 of the same file for the same reason, for $info->image->__toString().