Fix: htmlentities() shouldn't be called with null

[fedeisas]

Fix: htmlentities(): Passing null to parameter #1 ($string) of type string is deprecated

• [X] I've run the tests with vendor/bin/phpunit
• [X] None of the tests were found failing
• [X] I've seen the coverage report at build/coverage/index.html
• [X] Not a single line left uncovered by tests
• [X] Any coding standards issues were fixed with vendor/bin/php-cs-fixer fix

[sanmai]

How can I get you to add unit test for this change?

[fedeisas]

@sanmai ✅

[fedeisas]

thanks @sanmai