MLangs: Fix GROUP_BY over-cloning its properties.
MLangs: Fix GROUP_BY over-cloning its properties.

jacksonic/foam,jacksonic/foam,mdittmer/foam,jlhughes/foam,jlhughes/foam,jacksonic/foam,foam-framework/foam,mdittmer/foam,jacksonic/foam,jlhughes/foam,mdittmer/foam,foam-framework/foam,foam-framework/foam,mdittmer/foam,foam-framework/foam,foam-framework/foam,jlhughes/foam