fix missing declare variable

Signed-off-by: Lorenzo Tanganelli <lorenzo.tanganelli@hotmail.it>

apps/theming/lib/ThemingDefaults.php

@@ -71,6 +71,7 @@ class ThemingDefaults extends \OC_Defaults {
 	private string $productName;
 	private string $url;
 	private string $color;
+	private string $docBaseUrl;
 
 	private string $iTunesAppId;
 	private string $iOSClientUrl;