Fix PHP Warning: strlen() expects parameter 1 to be string, object given

program/steps/addressbook/export.inc

@@ -89,7 +89,7 @@ while ($result && ($row = $result->next())) {
         foreach ($row as $key => $values) {
             list($field, $section) = explode(':', $key);
             foreach ((array)$values as $value) {
-                if (is_array($value) || strlen($value))
+                if (is_array($value) || @strlen($value))
                     $vcard->set($field, $value, strtoupper($section));
             }
         }