gs-app-context-bar: Make sure symbolic icons are used here
I noticed my theme (Blue Menta) picks a regular icon instead of the symbolic icon on the gs-app-context-bar. See the Safety tile here:
It doesn't do that everywhere, as the screenshot shows. Maybe it's due to the icon size, I do not know, but I think it makes sense to force the symbolic icon usage here, to be consistent with the design (and between tiles).