Centering of components in horizontal layout

Test case: https://jasonbase.com/things/A2GK

The first template has as the first item a horizontal layout with space - button - button - space. The idea is to center the buttons. The last space components doesn't render. If I change type from space to label it works as expected pushing the buttons into the center.

Updated the json to be smaller. Also tested on the Jason app, this isn't a regression, it doesn't work on master either.

Start with the linked Jasonbase test case and reproduce the horizontal layout containing space, button, button, and space on the Jason app or master. Trace how horizontal layouts render trailing space components. Done means the final space renders consistently and the two buttons are centered, with the provided smaller JSON still reproducing the corrected behavior.

Written by the indexing model from the issue text.