private function checkDefaultTreeBlocksExist(): void
    {
        $has_blocks = DB::table('block')
            ->where('gedcom_id', '=', -1)
            ->exists();

        // No default settings?  Create them.
        if (!$has_blocks) {
            foreach (['main', 'side'] as $location) {
                foreach (self::DEFAULT_TREE_PAGE_BLOCKS[$location] as $block_order => $class) {
                    $module_name = $this->module_service->findByInterface($class)->first()->name();

                    DB::table('block')->insert([
                        'gedcom_id'   => -1,
                        'location'    => $location,
                        'block_order' => $block_order,
                        'module_name' => $module_name,
                    ]);
                }
            }
        }
    }