fix: Argument #2 () cannot be null

src/Webservice/Help.php

@@ -1,6 +1,7 @@
 <?php
 namespace Bsr\Webservice;
 
+use Bsr\Webservice\Exception\BugException;
 use Bsr\Webservice\Exception\WebException;
 use Bsr\Webservice\Formatter\Html;
 
@@ -16,7 +17,7 @@ class Help
      * @param mixed $ws
      * @param sting $func the function to be presented
      */
-    private static function func($ws, $func)
+    private static function func($ws, string $func)
     {
         try {
             $rm = new \ReflectionMethod($ws, $func);

src/Webservice/WebService.php

@@ -51,7 +51,9 @@ abstract class WebService
             $data["error"]["reason"] = $e->getMessage();
             $data["error"]["name"] = $e->getName();
 
+            if ($this->func !== null) {
                 $data['extra'] = Help::exception($e, $this, $this->func);
+            }
 
             $this->status = 400;