Fix a PHP 8.2 deprecation notice from StaticView, a=chris

diff --git a/src/views/StaticView.php b/src/views/StaticView.php
index 34e4ff39b..e6b9dbcd8 100644
--- a/src/views/StaticView.php
+++ b/src/views/StaticView.php
@@ -44,6 +44,12 @@ class StaticView extends View
      * @var string
      */
     public $layout = "web";
+    /**
+     * Properties of a wiki page related to the head of the output HTML
+     * document.
+     * @var array
+     */
+    public $head_objects;
     /**
      * Draws wiki page in a more static fashion.
      *