Favor SkinTemplateNavigation::Universal

This hook is run on every page. The SkinTemplateNavigation hook
counter intutively is run only on pages which can exist. I think
it's clearer if we only use SkinTemplateNavigation::Universal hook
and keep the logic for when it runs inside our own code.

Bug: T255319
Change-Id: I0835074a6cadf6e9bdcc45299de37dd9328bf9b2

includes/Hooks.php

@@ -119,9 +119,11 @@ class Hooks {
 	 * @param array &$content_navigation
 	 */
 	public static function onSkinTemplateNavigation( $sk, &$content_navigation ) {
+		$title = $sk->getRelevantTitle();
 		if (
+			$sk->getConfig()->get( 'VectorUseIconWatch' ) &&
 			$sk->getSkinName() === 'vector' &&
-			$sk->getConfig()->get( 'VectorUseIconWatch' )
+			$title && $title->canExist()
 		) {
 			$key = null;
 			if ( isset( $content_navigation['actions']['watch'] ) ) {

skin.json

@@ -59,7 +59,7 @@
 		"SkinPageReadyConfig": "Vector\\Hooks::onSkinPageReadyConfig",
 		"GetPreferences": "Vector\\Hooks::onGetPreferences",
 		"PreferencesFormPreSave": "Vector\\Hooks::onPreferencesFormPreSave",
-		"SkinTemplateNavigation": "Vector\\Hooks::onSkinTemplateNavigation",
+		"SkinTemplateNavigation::Universal": "Vector\\Hooks::onSkinTemplateNavigation",
 		"LocalUserCreated": "Vector\\Hooks::onLocalUserCreated",
 		"OutputPageBodyAttributes": "Vector\\Hooks::onOutputPageBodyAttributes",
 		"MakeGlobalVariablesScript": "Vector\\Hooks::onMakeGlobalVariablesScript"

tests/phpunit/integration/VectorHooksTest.php

@@ -289,6 +289,7 @@ class VectorHooksTest extends \MediaWikiTestCase {
 			'wgVectorUseIconWatch' => true
 		] );
 		$skin = new SkinVector( [ 'name' => 'vector' ] );
+		$skin->getContext()->setTitle( Title::newFromText( 'Foo' ) );
 		$contentNavWatch = [
 			'actions' => [
 				'watch' => [ 'class' => 'watch' ],