Pass variable into global scope and determine if query output is null Laravel - localization

Question

I've translation models and I want to run Global query scope that determine the current locale and return the corresponding value upon it or fall back into English if the translation doesn't exist in DB.
I've created a global scope for this purpose and its running good without the ability to fall back into English, so some pages crashes since I'm trying to get property of NULL, and I tried passing some value, but inside the builder I can't determine if the query is going to return null.
How may achieve such thing in Laravel?
my code as follows:
trait WhereLanguage {
/**
* Boot the Where Language trait for a model.
*
* #return void
*/
public static function bootWhereLanguage()
{
static::addGlobalScope(new WhereLanguageScope);
}
}
and the Scope file:
class WhereLanguageScope implements ScopeInterface {
/**
* Apply the scope to a given Eloquent query builder.
*
* #param \Illuminate\Database\Eloquent\Builder $builder
* #param \Illuminate\Database\Eloquent\Model $model
*/
public function apply(Builder $builder, Model $model)
{
$this->addWhereLang($builder);
}
/**
* Remove the scope from the given Eloquent query builder.
*
* #param \Illuminate\Database\Eloquent\Builder $builder
* #param \Illuminate\Database\Eloquent\Model $model
*
* #return void
*/
public function remove(Builder $builder, Model $model)
{
$query = $builder->getQuery();
foreach ((array) $query->wheres as $key => $where)
{
// If the where clause is a soft delete date constraint, we will remove it from
// the query and reset the keys on the wheres. This allows this developer to
// include deleted model in a relationship result set that is lazy loaded.
if ($where['column'] == 'lang_id')
{
unset($query->wheres[$key]);
$query->wheres = array_values($query->wheres);
}
}
}
/**
* Extend Builder with custom method.
*
* #param \Illuminate\Database\Eloquent\Builder $builder
*
*/
protected function addWhereLang(Builder $builder)
{
$builder->macro('whereLang', function(Builder $builder)
{
// here 1 is ID for English,
// 48 Arabic, 17 Netherlands...etc
// and It was the App:currentlocale() passed into Language model to determine the ID of current locale.
// but for testing now I hard coded it with ID of 48
$builder->where('lang_id','=','48');
return $builder;
});
}
}
Usage example:
$title = $centre->translations()->whereLang()->first()->name;
Where Centre is my model without localization, and translation is the name of method that handling the relation between Centre & CentreTranslation.
btw I don't want to pass variable obligately.