Highlight doesn't work for 'is not empty' and 'is not defined'

[dmitrach]

Twig support 'is not' and 'empty':
https://twig.symfony.com/doc/2.x/templates.html#test-operator
https://twig.symfony.com/doc/2.x/tests/empty.html

But for the combination the highlight doesn't work. Also it doesn't work for 'defined'.

Empty: 
{{ post.content is empty ? 'action-true' : 'action-false' }} It works.
{{ post.content is not empty ? 'action-true' : 'action-false' }} It doesn't work. It equals {{ not post.content ? 'action' }}
{{ not post.content is empty ? 'action-true' : 'action-false' }} It works.

Defined:
{{ test is not defined ? 'action-when-undefined' }} It doesn't work. It doesn't equal {{ not test ? 'action' }} and {{ test is empty ? 'action' }}
{{ not test is defined ? 'action-when-undefined' }} It works.

{# Defines the variable #}
{% set test = false %}

They are correct expressions.