Impossible to invoke a method ("children") on a null variable.
<i>{{ spContent.artist() }}</i>
</h3>
<a href="{{ aristSpectacle.parent().url }}" class="stretched-link"></a>
</div>
{% endfor %}
{% endfor %}
{% set actualites = site.page('actualitesartistes').children().listed().sortBy('start_date', 'esc') %}
{% for actualite in actualites %}
{% set aristActualites = actualite.associated_artists().toStructure().filterBy('associated_artist', page.uid) %}
{% for artistActualite in aristActualites %}
{% set datetoday = "now"|date("Y-m-d") %}
{% set today = "now"|date("U") %}
{% set arContent = artistActualite.parent().content() %}