Can now drag an item out of inventory and drop on the ground, then pick it back up, and put it in a loot container, and then back again. Still buggy but working for now.

gui/dnd_loot.cpp

@@ -114,6 +114,8 @@ namespace gui {
       case MOUSE_DROP: {
         auto& grab = $status_ui.$gui.get<guecs::GrabSource>(*$grab_source);
         grab.commit();
+        bool dropped = $status_ui.drop_item(grab.world_entity);
+        dbc::check(dropped, "DROP FAILED!");
         END(Event::CLOSE);
        } break;
       default: