EmptyIdException to make sure we get the right in catch

classes/Managed_DataObject.php

@@ -384,7 +384,7 @@ abstract class Managed_DataObject extends Memcached_DataObject
     static function getByID($id)
     {
         if (empty($id)) {
-            throw new ServerException('Empty ID on lookup');
+            throw new EmptyIdException(get_called_class());
         }
         // getByPK throws exception if id is null
         // or if the class does not have a single 'id' column as primary key

lib/emptyidexception.php

@@ -0,0 +1,38 @@
+<?php
+/**
+ * StatusNet, the distributed open-source microblogging tool
+ *
+ * Class for an exception when a database lookup returns no results
+ *
+ * PHP version 5
+ *
+ * LICENCE: This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @category  Exception
+ * @package   GNUsocial
+ * @author    Mikael Nordfeldth <mmn@hethane.se>
+ * @copyright 2013 Free Software Foundation, Inc.
+ * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPLv3
+ * @link      http://www.gnu.org/software/social/
+ */
+
+if (!defined('GNUSOCIAL')) { exit(1); }
+
+class EmptyIdException extends ServerException
+{
+    public function __construct($called_class)
+    {
+        parent::__construct(sprintf(_('Empty ID value was given to query for a "%s" object'), $called_class));
+    }
+}