Use null coalesce operator instead of ternary operator

Problem/Motivation

Many files from module shows the error "Use null coalesce operator instead of ternary operator" when verifying code standards with PHPCS.

Steps to reproduce

Run the following command at module folder:
phpcs --standard=Drupal,DrupalPractice --extensions=php,module,inc,install,test,profile,theme,css,info,md,yml *

Proposed resolution

Change the code to use coalesce operator.