Front end Fatal error rendering tag cloud for unregistered taxonomy

[bobbingwide]

While attempting to check that oik.css wasn't inadvertently affecting the style changes noticed when using Gutenberg-source ( latest trunk) I deactivated oik. This prevented the custom taxonomies from being registered which produced a Fatal error trying to display the tag cloud.

Warning: Attempt to read property "labels" on bool in C:\apache\htdocs\bigram\wp-includes\taxonomy.php on line 582

Fatal error: Uncaught Error: Attempt to assign property "labels" on bool in C:\apache\htdocs\bigram\wp-includes\taxonomy.php:582
Stack trace:

#0 C:\apache\htdocs\wordpress\wp-content\plugins\gutenberg-wordpress-source\build\block-library\blocks\tag-cloud.php(24): get_taxonomy_labels(false) 
#1 C:\apache\htdocs\wordpress\wp-content\plugins\gutenberg-wordpress-source\lib\compat.php(136): gutenberg_render_block_core_tag_cloud(Array, '', Object(WP_Block)) 
#2 C:\apache\htdocs\bigram\wp-includes\class-wp-block.php(221): {closure}(Array, '', Object(WP_Block)) 
#3 C:\apache\htdocs\bigram\wp-includes\class-wp-block.php(211): WP_Block->render() 
#4 C:\apache\htdocs\bigram\wp-includes\class-wp-block.php(211): WP_Block->render() 
#5 C:\apache\htdocs\bigram\wp-includes\class-wp-block.php(211): WP_Block->render() 
#6 C:\apache\htdocs\bigram\wp-includes\blocks.php(799): WP_Block->render() 
#7 C:\apache\htdocs\bigram\wp-includes\blocks.php(837): render_block(Array) 
#8 C:\apache\htdocs\wordpress\wp-content\plugins\gutenberg-wordpress-source\build\block-library\blocks\template-part.php(100): do_blocks('<!-- wp:group {...') 
#9 C:\apache\htdocs\wordpress\wp-content\plugins\gutenberg-wordpress-source\lib\compat.php(136): gutenberg_render_block_core_template_part(Array, '', Object(WP_Block)) 
#10 C:\apache\htdocs\bigram\wp-includes\class-wp-block.php(221): {closure}(Array, '', Object(WP_Block)) 
#11 C:\apache\htdocs\bigram\wp-includes\blocks.php(799): WP_Block->render() 
#12 C:\apache\htdocs\bigram\wp-includes\blocks.php(837): render_block(Array) 
#13 C:\apache\htdocs\wordpress\wp-content\plugins\gutenberg-wordpress-source\lib\full-site-editing\template-loader.php(182): do_blocks('<!-- wp:templat...') 
#14 C:\apache\htdocs\wordpress\wp-content\plugins\gutenberg-wordpress-source\lib\template-canvas.php(12): gutenberg_get_the_template_html() 
#15 C:\apache\htdocs\bigram\wp-includes\template-loader.php(106): include('C:\\apache\\htdoc...') 
#16 C:\apache\htdocs\bigram\wp-blog-header.php(19): require_once('C:\\apache\\htdoc...') 
#17 C:\apache\htdocs\bigram\index.php(17): require('C:\\apache\\htdoc...') 
#18 {main} thrown in C:\apache\htdocs\bigram\wp-includes\taxonomy.php on line 582

[bobbingwide]

This wasn't a problem on s.b/bigram but it is a problem on s.b/wp55/sb where I'm testing the template file only version of the theme.

[bobbingwide]

The problem still occurs when the taxonomy is not registered and the tag-cloud override is not enabled.
This state of affairs occurs can be created by deactivating the oik plugin.

Warning: Attempt to read property "labels" on bool in C:\apache\htdocs\wp55\wp-includes\taxonomy.php on line 652

Fatal error: Uncaught Error: Attempt to assign property "labels" on bool in C:\apache\htdocs\wp55\wp-includes\taxonomy.php:652 Stack trace:

#0 C:\apache\htdocs\wp55\wp-content\plugins\gutenberg\build\block-library\blocks\tag-cloud.php(25): get_taxonomy_labels(false)
#1 C:\apache\htdocs\wp55\wp-content\plugins\gutenberg\lib\compat.php(132): gutenberg_render_block_core_tag_cloud(Array, '', Object(WP_Block))
#2 C:\apache\htdocs\wp55\wp-includes\class-wp-block.php(255): {closure}(Array, '', Object(WP_Block))
#3 C:\apache\htdocs\wp55\wp-includes\class-wp-block.php(241): WP_Block->render()
#4 C:\apache\htdocs\wp55\wp-includes\class-wp-block.php(241): WP_Block->render()
#5 C:\apache\htdocs\wp55\wp-includes\class-wp-block.php(241): WP_Block->render()
#6 C:\apache\htdocs\wp55\wp-includes\blocks.php(883): WP_Block->render()
#7 C:\apache\htdocs\wp55\wp-includes\blocks.php(921): render_block(Array)
#8 C:\apache\htdocs\wordpress\wp-content\themes\sb\includes\template-part.php(107): do_blocks('<!-- wp:group {...')
#9 C:\apache\htdocs\wp55\wp-content\plugins\gutenberg\lib\compat.php(132): sb_render_block_core_template_part(Array, '<!-- wp:group {...', Object(WP_Block))
#10 C:\apache\htdocs\wp55\wp-includes\class-wp-block.php(255): {closure}(Array, '', Object(WP_Block))
#11 C:\apache\htdocs\wp55\wp-includes\blocks.php(883): WP_Block->render()
#12 C:\apache\htdocs\wp55\wp-includes\blocks.php(921): render_block(Array)
#13 C:\apache\htdocs\wp55\wp-includes\block-template.php(240): do_blocks('<!-- wp:oik-sb/...')
#14 C:\apache\htdocs\wp55\wp-includes\template-canvas.php(12): get_the_block_template_html()
#15 C:\apache\htdocs\wp55\wp-includes\template-loader.php(106): include('C:\\apache\\htdoc...')
#16 C:\apache\htdocs\wp55\wp-blog-header.php(19): require_once('C:\\apache\\htdoc...')
#17 C:\apache\htdocs\wp55\index.php(17): require('C:\\apache\\htdoc...')
#18 {main}
  thrown in <b>C:\apache\htdocs\wp55\wp-includes\taxonomy.php</b> on line <b>652</b><br />

It's a bug in Gutenberg which has now made its way into core.
This confirms that the tag-cloud override is still necessary; it implements logic to check if the taxonomy is registered.
This bug is a follow on to PR 16098 which was the fix to WordPress/gutenberg#13932

if ( ! $tag_cloud ) {
        $taxonomy = get_taxonomy($attributes['taxonomy']);
        if ($taxonomy) {
            $labels = get_taxonomy_labels(get_taxonomy($attributes['taxonomy']));
            $tag_cloud = esc_html(
                sprintf(
                /* translators: %s: taxonomy name */
                    __('Your site doesn’t have any %s, so there’s nothing to display here at the moment.'),
                    strtolower($labels->name)
                )
            );
        } else {
            $tag_cloud = esc_html(
                sprintf(
                /* translators: %s: taxonomy name */
                    __('Tag cloud not displayed. Taxonomy %s is not registered.'), $attributes['taxonomy']

                )
            );
        }

    }