Add min_body configuration option for post too short check

inc/config.php

@@ -488,6 +488,8 @@
 
 	// Maximum post body length.
 	$config['max_body'] = 1800;
+	// Minimum post body length.
+	$config['min_body'] = 0;
 	// Maximum number of post body lines to show on the index page.
 	$config['body_truncate'] = 15;
 	// Maximum number of characters to show on the index page.

post.php

@@ -730,6 +730,8 @@ if (isset($_POST['delete'])) {
 			error(sprintf($config['error']['toolong'], 'subject'));
 		if (!$mod && mb_strlen($post['body']) > $config['max_body'])
 			error($config['error']['toolong_body']);
+		if (!$mod && mb_strlen($post['body']) > 0 && mb_strlen($post['body']) < $config['min_body'])
+			error($config['error']['tooshort_body']);
 		if (mb_strlen($post['password']) > 20)
 			error(sprintf($config['error']['toolong'], 'password'));
 	}