atto_styles: Try parent node if no class attribute when removing styles

[tonyjbutler]

This fixes a bug where attempting to remove a particular style sometimes fails.

[abias]

Hi Tony,

thank you for this pull request and sorry for your patience with me coming back to you.

Could you please give me some background information / steps to reproduce which wrong behavior this pull request tries to solve?

Thanks,
Alex

[tonyjbutler]

Hi Alex,

To be honest I can't remember the exact conditions necessary to reproduce this, but I think if you apply multiple styles to the same text you can get into a situation where nested elements are created, with different classes applied to each, and then only the class attribute on the innermost element can be removed with the button so you end up having to edit the HTML directly to get rid of them all.

Hope this helps.

Thanks,
Tony