Add language settings button inside dropdown for non-content pages

Bug: T316559
Change-Id: Ifdf2a529b30e5a2df8867b606a525c9f7b3bdb6c

includes/Hooks.php

@@ -170,6 +170,10 @@ class Hooks implements
 		if ( $this->isEnabled() ) {
 			// Enable UI language selection for the user.
 			$out->addModules( 'ext.uls.interface' );
+
+			$templateData = $skin->getTemplateData();
+			$isLanguageSelectorEmpty = $templateData[ 'data-lang-btn' ][ 'is-language-selector-empty' ] ?? false;
+			$config[ 'wgULSisLanguageSelectorEmpty' ] = $isLanguageSelectorEmpty;
 		}
 
 		// This is added here, and not in onResourceLoaderGetConfigVars to allow skins and extensions