Fixing fatal error.

plugin/clockworksms/lib/clockworksms.lib.php

@@ -59,7 +59,8 @@ class Clockworksms
     private function getMobilePhoneNumberById($userId)
     {
         require_once api_get_path(LIBRARY_PATH).'extra_field.lib.php';
-        $mobilePhoneNumberExtraField = (new ExtraField('user'))->get_handler_field_info_by_field_variable('mobile_phone_number');
+        $mobilePhoneNumberExtraField = new ExtraField('user');
+        $mobilePhoneNumberExtraField = $mobilePhoneNumberExtraField->get_handler_field_info_by_field_variable('mobile_phone_number');
         require_once api_get_path(LIBRARY_PATH).'extra_field_value.lib.php';
         $mobilePhoneNumberExtraFieldValue = (new ExtraFieldValue('user'))->get_values_by_handler_and_field_id($userId, $mobilePhoneNumberExtraField['id']);
         return $mobilePhoneNumberExtraFieldValue['field_value'];