Index: src/wp-admin/includes/plugin.php
===================================================================
--- src/wp-admin/includes/plugin.php	(revision 27472)
+++ src/wp-admin/includes/plugin.php	(working copy)
@@ -991,7 +991,7 @@
 		add_action( $hookname, $function );
 
 	if ( empty($icon_url) ) {
-		$icon_url = 'none';
+		$icon_url = 'dashicons-admin-generic';
 		$icon_class = 'menu-icon-generic ';
 	} else {
 		$icon_url = set_url_scheme( $icon_url );