Deprecation errors with PHP 8

WP Recipe Maker causes deprecation errors with PHP 8. The problem is this:

add_submenu_page( null, __( 'Import Recipes', 'wp-recipe-maker' ), __( 'Import Recipes', 'wp-recipe-maker' ), WPRM_Settings::get( 'features_import_access' ), 'wprm_import', array( __CLASS__, 'import_page_template' ) );
add_submenu_page( null, __( 'Search Recipes', 'wp-recipe-maker' ), __( 'Search Recipes', 'wp-recipe-maker' ), WPRM_Settings::get( 'features_import_access' ), 'wprm_import_search', array( __CLASS__, 'import_search_page_template' ) );
add_submenu_page( null, __( 'Importing Recipes', 'wp-recipe-maker' ), __( 'Importing Recipes', 'wp-recipe-maker' ), WPRM_Settings::get( 'features_import_access' ), 'wprm_importing', array( __CLASS__, 'importing_recipes' ) );

Using null as the first parameter for add_submenu_page() causes deprecation warnings with PHP 8 as strpos() and str_replace() no longer accept null values. You can replace the null values with empty strings to eliminate the warnings.