Disable coverage instead of a blank string

Author: desrosj

.github/workflows/reusable-phpunit-tests-v4.yml

@@ -147,7 +147,7 @@ jobs:
         uses: shivammathur/setup-php@20529878ed81ef8e78ddf08b480401e6101a850f # v2.35.3
         with:
           php-version: '${{ inputs.php }}'
-          coverage: ${{ inputs.coverage-report && 'xdebug' || '' }}
+          coverage: ${{ inputs.coverage-report && 'xdebug' || 'none' }}
           tools: wp-cli
 
       # Since Composer dependencies are installed using `composer update` and no lock file is in version control,