Laravel Attempt to read property “alias” on null

Route::get('catalog/{catname}', [MainController::class, 'getCatalog'])->name('catalog.page');
Route::get('catalog/{catname}/{alias}', [MainController::class, 'getItemsForList'])->name('catalog.view.item');

When I click on the link /catalog/table/table-black-and-white, I get an error

Attempt to read property "alias" on null

During development, I connected the database via belongsToMany

AppModelsCatalog

public function items() : BelongsToMany
{
return $this->belongsToMany(Item::class);
}

AppModelsItem
public function catalogs() : BelongsToMany
{
return $this->belongstoMany(Catalog::class);
}

The controller has two entries for outputting information

public function getCatalog($alias)
    {
        $cats = Catalog::where('alias', $alias)->first();
        $cats->items;
        return view('template.sait.page.catalog', compact('cats'))->with('alias', $alias);
    }

    public function getItemsForList($alias)
    {
        $data = Item::where('alias', $alias)->with('catalogs')->first();
        return view('template.sait.page.catalog.view', compact('data'))->with('alias', $alias);
    }

And in the view I display it like this:

@foreach($cats->items as $item)
.....
.....
<a href="{{route(''catalog.view.item'', $item->alias)}}">env</a>

As far as I understand, there is an error in my controller, and apparently I also do not fully indicate the route in the view, since sometimes I still get the error of missing “alias” field