Update ResponseValidator.php

Issue kleiram#35
I debugged the behaviour, the response from transmission rpc was fine, it was sending result object as "duplicate torrent" and argument object was empty. 
the validator for addtorrent was parsing it as invalid because of absence of torrent-duplicate object inside arguments.
I have fixed it and requested a pull.

Author: bilalghouri

lib/Transmission/Util/ResponseValidator.php

@@ -59,15 +59,26 @@ public static function validateGetResponse(\stdClass $response)
      */
     public static function validateAddResponse(\stdClass $response)
     {
-        $fields = array('torrent-added', 'torrent-duplicate');
+        // fix for issue #35
+        if ($response -> result == 'success' &&
+			isset ($response->arguments -> {torrent-added}) &&
+			count($response->arguments -> {torrent-added}))
+		{
+			return $response->arguments -> {torrent-added};
+		}
+		if ($response -> result == 'duplicate torrent')
+			return $response -> result;
+		
+		
+        /*$fields = array('torrent-added', 'torrent-duplicate');
 
         foreach ($fields as $field) {
             if (isset($response->arguments) &&
                 isset($response->arguments->$field) &&
                 count($response->arguments->$field)) {
                 return $response->arguments->$field;
             }
-        }
+        }*/
 
         throw new \RuntimeException('Invalid response received from Transmission');
     }