save className of multiple SelectControl values

[robertosimoes]

Thank you very much for this example plugin, it's helping me learn Gutenberg.

Your example of multiple SelectControl: https://github.com/liip/extend-block-example-wp-plugin/blob/feat/additional-attribute-logic/assets/js/spacing-control.js

I noticed that only the last attribute .has-spacing-bottom-$ is saved. The .has-spacing-top-$ is ignored.

I'm trying to fix it without success. Could you give me at least a hint on how to solve this issue?

Thanks and Cheers!