Example composite AJAX Error if rendered not as table

If you render a example composite not as a table, click on Add/Remove button raises an Ajax Error

AjaxError: 
An AJAX HTTP error occurred.
HTTP Result Code: 200
Debugging information follows.
Path: /form/webform-example-composite?ajax_form=1
StatusText: OK
ResponseText: 
Fatal error:  Call to undefined function _template_preprocess_webform_composite() in /home/r2zi0/www/modules/webform/modules/webform_example_composite/webform_example_composite.module on line 32  js_g6BvtjuwxIS_Nn7ebv9__1bD4YDu4f_1XpB2O6ZWzSI.js:2335:32

tested on a clean installation on simplytest.me.

Non-example composites work fine if rendered not as a able.