Swiper formatter breaks on custom fields in views

Problem/Motivation

Hello, I try to use Swiper formatter for my view where I used Global "Custom text" field, and Swiper don't open settings in such configuration.

Steps to reproduce

Try to add Custom text field to the Swiper view.

Proposed resolution

The problem is here: SwiperFormatterStyle.php

$field_storage_definitions = $this->entityFieldManager->getFieldStorageDefinitions($field->definition['entity_type']);

You need to wrap it up with

if (!empty($field->definition['entity_type'])) {
  $field_storage_definitions = $this->entityFieldManager->getFieldStorageDefinitions($field->definition['entity_type']);
}