Invalid header value type; must be a string or numeric; received NULL Laravel

I have just upgraded from laravel 5.8 to 6.0.0 and I'm tying to store images to the database but I get an error Invalid header value type; must be a string or numeric; received NULL from vendor/zendframework/zend-diactoros/src/HeaderSecurity.php" line: 139. Does anyone have an idea why I'm getting this?

Controller

     if($request->hasFile('files')){

        $store_file = [];
        $files = $request->file('files');
        foreach ($files as $file) {
            $images = $file->store('public/photos');

            $store_file[] = [

                'product_id' => $product->id,
                'filename' =>  $images
            ];
        }

        ProductsPhoto::insert($store_file);
    }

via Chebli Mohamed