fix path handling in `action_link()`, fixes #1188

Closes #1188

Merge request studip/studip!704

app/controllers/studip_controller.php

@@ -740,10 +740,7 @@ abstract class StudipController extends Trails_Controller
      */
     public function action_link($action)
     {
-        $arguments = func_get_args();
-        array_unshift($arguments, $this->controller_path());
-
-        return $this->link_for(...$arguments);
+        return htmlReady($this->action_url(...func_get_args()));
     }
 
     /**

tests/unit/lib/classes/StudipControllerTest.php

@@ -76,6 +76,12 @@ final class StudipControllerTest extends Codeception\Test\Unit
             $expected,
             $this->getRelativeURL($url)
         );
+
+        $link = $this->getController()->action_link(...$args);
+        $this->assertEquals(
+            htmlspecialchars($expected),
+            $this->getRelativeURL($link)
+        );
     }
 
     /**