Hi. I encountered this weird issue that I don't seem to find anywhere being mentioned.

{% set test2 = 'text 2' %}
{{ dump(test1) }}
{{ test1 ? test1 : test2 }}

This does not render any text. If test1 was set, it would output test1, as expected.

This does output text 2:
{{ test1 ?: test2 }}

Tried this on 1.17.1 as well.
PHP twig renders as expected.