internal.py

                bpy.ops.curve.select_all(action='DESELECT')
                if prev_layer[j].type == 'POLY':
                    prev_layer[j].points[-1].select = True
                else:
                    prev_layer[j].bezier_points[-1].select_control_point = True
                if next_layer[j].type == 'POLY':
                    next_layer[j].points[0].select = True
                else:
                    next_layer[j].bezier_points[0].select_control_point = True
                bpy.ops.curve.make_segment()
    bpy.ops.curve.select_all(action='DESELECT')