select only input checkbox el for fieldset toggle

there is also an hidden element and this causes some problems

commonjs/frontend-form/field/field-set.js

@@ -3,7 +3,7 @@ var Field = require('kwf/frontend-form/field/field');
 var kwfExtend = require('kwf/extend');
 var onReady = require('kwf/on-ready');
 
-onReady.onRender('div.kwfUp-kwfFormContainerFieldSet fieldset > legend > input', function fieldSet(c)
+onReady.onRender('div.kwfUp-kwfFormContainerFieldSet fieldset > legend > input[type="checkbox"]', function fieldSet(c)
 {
     if (!c.get(0).checked) {
         c.closest('fieldset').addClass('kwfFormContainerFieldSetCollapsed');