Customize: Prevent PHP notice in Customizer when using block theme.

Use the `customize_panel_active` filter to deactivate the Menus panel instead of overriding the `check_capabilities` method. This ensures the panel remains registered but is still hidden.

See #54888.
Fixes #54905.


git-svn-id: https://develop.svn.wordpress.org/trunk@54419 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/theme.php

@@ -4257,4 +4257,23 @@ function _add_default_theme_supports() {
 	add_theme_support( 'automatic-feed-links' );
 
 	add_filter( 'should_load_separate_core_block_assets', '__return_true' );
+
+	/*
+	 * Remove the Customizer's Menus panel when block theme is active.
+	 */
+	add_filter(
+		'customize_panel_active',
+		static function ( $active, WP_Customize_Panel $panel ) {
+			if (
+				'nav_menus' === $panel->id &&
+				! current_theme_supports( 'menus' ) &&
+				! current_theme_supports( 'widgets' )
+			) {
+				$active = false;
+			}
+			return $active;
+		},
+		10,
+		2
+	);
 }