fix for tree indentation issue

[krishnasai057]

Hi Oli,

There is an issue with the indentation of tree when expanded
more details of issue and how to replicate can be found here - #4511.

This PR will fix the indentation issue when tree is expanded.

[olifolkerd]

Hey @krishnasai057

Thanks for the PR, and love the idea of the fix, but im afraid the calculation maths does not account for any CSS marging/padding that may be applied to the elements outside of the javascript, which is why those were included in the first place.

Please account for this in your logic and i would be happy to consider this for inclusion.

Cheers

Oli :)