i am getting this error while generating PDF with laravel

Undefined offset: 1 (View: /var/www/html/bds/livesystems/aegispest.bigdreams.in/resources/views/pdf/normal_invoice_table.blade.php) (View: /var/www/html/bds/livesystems/aegispest.bigdreams.in/resources/views/pdf/normal_invoice_table.blade.php)

this is the error I'm getting

  <div class="col-xs-2 b-r">
        <h4 class="text-center"> <?php echo e(Company::frequency_no($qtys[$i]) ?? 1); ?> <?php echo e($invoice->category == 'custom' ?  '' :'Service'); ?><?php echo e((Company::frequency_no($qtys[$i]) ?? 1) > 1 ? 's':''); ?><?php echo e($invoice->category == 'custom' ? ($unit_name[$i] ?? '') :''); ?></h4>

via Chebli Mohamed