Manage the case where `$_SERVER[‘HTTP_USER_AGENT’]` is undefined

Hi,

In the file /wp-content/plugins/eps-301-redirects/eps-301-redirects.php, line 969:

$last['user_agent'] = @strip_tags($_SERVER['HTTP_USER_AGENT']);

it displays two warnings in the log file when HTTP_USER_AGENT is undefined:

PHP Error: [2] Undefined array key "HTTP_USER_AGENT" in /wp-content/plugins/eps-301-redirects/eps-301-redirects.php on line 969
Stack trace:
#0 /wp-content/plugins/eps-301-redirects/eps-301-redirects.php(969): custom_error_handler(integer, string, string, integer)
#1 /wp-includes/class-wp-hook.php(324): EPS_Redirects->check_404(string)
#2 /wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(boolean, array)
#3 /wp-includes/plugin.php(517): WP_Hook->do_action(array)
#4 /wp-includes/template-loader.php(13): do_action(string)
#5 /wp-blog-header.php(19): require_once(string)
#6 /index.php(17): require(string)
PHP Error: [8192] strip_tags(): Passing null to parameter #1 ($string) of type string is deprecated in /wp-content/plugins/eps-301-redirects/eps-301-redirects.php on line 969
Stack trace:
#1 /wp-content/plugins/eps-301-redirects/eps-301-redirects.php(969): strip_tags(NULL)
#2 /wp-includes/class-wp-hook.php(324): EPS_Redirects->check_404(string)
#3 /wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(boolean, array)
#4 /wp-includes/plugin.php(517): WP_Hook->do_action(array)
#5 /wp-includes/template-loader.php(13): do_action(string)
#6 /wp-blog-header.php(19): require_once(string)
#7 /index.php(17): require(string)

I’m using 301 Redirects v2.76, WordPress 6.5.5 and PHP 8.1.