Display enum case signature only if there is a value.

Author: adriendupuis

tools/php_api_ref/.phpdoc/template/components/enum-case.html.twig

@@ -2,7 +2,7 @@
     {% embed 'components/content-header.html.twig' with { node: case, anchor: 'enumcase_' ~ case.name, anchor_link: link(case), header_tag: 'h3' } %}
     {% endembed %}
     {% include 'components/summary.html.twig' with { node: case } %}
-    {% include 'components/enum-case-signature.html.twig' with { node: case } %}
+    {% if case.value %}{% include 'components/enum-case-signature.html.twig' with { node: case } %}{% endif %}
     {% include 'components/deprecation.html.twig' with { node: case } %}
     {% include 'components/description.html.twig' with { node: case } %}
     {% include 'components/description.html.twig' with { node: case.var[0] } %}