webix#2.4 ajax issue

webix.ajax().headers({
                "Content-type": "application/json"
            })["post"](url, params, ajaxCallback);

// when the mode is post, Content-type will be replaced by 'application/x-www-form-urlencoded'

I can confirm the issue.

Fix will be included in the next build ( custom content-type will not be overridden anymore) Fixed build will be available till the end of this week.

Thanks.