Fix RelationNotFoundException when including undefined relation
[2017-01-13 17:05:15] local.ERROR: Illuminate\Database\Eloquent\RelationNotFoundException: Call to undefined relationship [user] on model [Netmon\Devices\Models\Device]. in /srv/http/netmonsc/api-server/vendor/laravel/framework/src/Illuminate/Database/Eloquent/RelationNotFoundException.php:20