fix: fixed the codeigniter routing for installations in subdirectories with the page index 3.

in the SiteURIFactory I checked that the requestUri is not null

Author: Franky5831

system/HTTP/SiteURIFactory.php

@@ -135,7 +135,7 @@ private function parseRequestURI(): string
 
         if($baseUri && !is_null($serverRequestUri)) $serverRequestUri = ltrim($serverRequestUri, $baseUri); // We remove the base Uri from the request URI if it exists, baseUri is the path to the subdirectory
         if($indexPage && !is_null($serverRequestUri)) $serverRequestUri = ltrim($serverRequestUri, "/" . $indexPage); // We remove the index page from the request URI if it exists
-        $serverRequestUri = "/". ltrim($serverRequestUri, '/'); // makes sure that the uri starts with a slash
+        if(!is_null($serverRequestUri)) $serverRequestUri = "/". ltrim($serverRequestUri, '/'); // makes sure that the uri starts with a slash
 
         if (
             $serverRequestUri === null