Currently the mimimap and selection panels are wrapped inside a “bottom panel” object. This is unnecessary, because it's centre on the centre of the bottom of the screen, and the selection panels' positions are already relative to that.
More importantly, it makes positioning the minimap more intuitive, because it's no longer relative to the bottom panels, making it easier for anyone to reposition the minimap in a mod (e.g. to the bottom left corner rather than attached to the left of the selection panels): without this patch they need to change both `session.xml` and `minimap_panel.xml`, with this patch they can ignore the former and only have to look at the latter.