Module incompatible with entities containing file fields without the getThirdPartySettings() function

Problem/Motivation

Entities outside of the standard node and media may have file fields that do not have the getThirdPartySettings() function. In those cases, PDF Preview Images's entity_presave hook prevents the entity from saving with the following error:

Error: Call to undefined method Drupal\Core\Field\BaseFieldDefinition::getThirdPartySetting() in pdf_preview_image_entity_presave()

Steps to reproduce

Install a module like section_library which defines an entity with a file field that does not use that method and attempt to save an entity.

Proposed resolution

Adding a check to make sure that the field definition has the getThirdPartySettings() function before calling it resolves this problem.