Url: Remove "/" in front of path if the url has a user parameter

refs #12133

library/Icinga/Web/Url.php

@@ -189,7 +189,7 @@ class Url
         if (isset($urlParts['path'])) {
             $urlPath = $urlParts['path'];
             if ($urlPath && $urlPath[0] === '/') {
-                if ($urlObject->isExternal()) {
+                if ($urlObject->isExternal() || isset($urlParts['user'])) {
                     $urlPath = substr($urlPath, 1);
                 } else {
                     $requestBaseUrl = $request->getBaseUrl();