Errors after installation

I get the following errors when installing this plugin and visiting the Settings page. I also get the error when testing a redirect.

Notice: Undefined index: _wpnonce in …/wp-content/plugins/all-404-redirect-to-homepage/option_page.php on line 10

Unable to save data!

Fatal error: Call to undefined function init_my_options() in …/wp-content/plugins/all-404-redirect-to-homepage/functions.php on line 49