Custom drag element of type button doesn't work

[gili-lumigo]

Subject of the issue

When using a custom handler to be an element of type button, The drag doesn't work at all.
It used to work on version 7.3.0 and stopped working on version 8.0.0.
From what I'm seeing, It's only for buttons... If I'm using other kinds of element (For ex. a span) it does work.

Your environment

• version of gridstack.js - 8.0.0
• which browser/OS - Chrome

Steps to reproduce

An example can be found here:
https://jsfiddle.net/gili_lumigo/t7vuycoL/3/

When the handler is of type button, The drag doesn't work and when it's of type span, It does

Expected behavior

Should work as prior to version 8 where the drag element works regardless of the element type.

[adumesny]

fixed in the next release. don't forget to donate if you find this lib useful.