Recalculate SLA supports after undo/redo in case SLA gizmo was active and had supports when the snapshot was taken

src/slic3r/Utils/UndoRedo.hpp

@@ -45,6 +45,7 @@ struct SnapshotData
 		SELECTED_SETTINGS_ON_SIDEBAR  = 2,
 		SELECTED_LAYERROOT_ON_SIDEBAR = 4,
 		SELECTED_LAYER_ON_SIDEBAR     = 8,
+        RECALCULATE_SLA_SUPPORTS      = 16
 	};
 };