Don't render unstableLocation if Nav block has ID (#36863)

* Don't try and render unstable location if Nav block has ID

* Reinstate condition for empty inner blocks

* Lint

* Show the unstableLocation menu items even if there are inner blocks, as long as there are items at that location.

Co-authored-by: Adam Zieliński <adam@adamziel.com>
Co-authored-by: Ben Dwyer <ben@scruffian.com>

packages/block-library/src/navigation/index.php

@@ -272,8 +272,15 @@ function render_block_core_navigation( $attributes, $content, $block ) {
 
 	$inner_blocks = $block->inner_blocks;
 
-	// If `__unstableLocation` is defined, create inner blocks from the classic menu assigned to that location.
-	if ( empty( $inner_blocks ) && array_key_exists( '__unstableLocation', $attributes ) ) {
+	// If `__unstableLocation` is defined and:
+	// - we have menu items at the defined location
+	// - we don't have a relationship to a `wp_navigation` Post (via `navigationMenuId`).
+	// ...then create inner blocks from the classic menu assigned to that location.
+	if (
+		array_key_exists( '__unstableLocation', $attributes ) &&
+		! array_key_exists( 'navigationMenuId', $attributes ) &&
+		! empty( gutenberg_get_menu_items_at_location( $attributes['__unstableLocation'] ) )
+	) {
 		$menu_items = gutenberg_get_menu_items_at_location( $attributes['__unstableLocation'] );
 		if ( empty( $menu_items ) ) {
 			return '';