fix model checkpoint merger tab failing to save model

            if save_as_half:

                theta_0[key] = theta_0[key].half()

    ckpt_dir = shared.cmd_opts.ckpt_dir or sd_models.model_path

    filename = primary_model_info.model_name + '_' + str(round(interp_amount, 2)) + '-' + secondary_model_info.model_name + '_' + str(round((float(1.0) - interp_amount), 2)) + '-' + interp_method.replace(" ", "_") + '-merged.ckpt'

    filename = filename if custom_name == '' else (custom_name + '.ckpt')

    output_modelname = os.path.join(shared.cmd_opts.ckpt_dir, filename)

    output_modelname = os.path.join(ckpt_dir, filename)

    print(f"Saving to {output_modelname}...")

    torch.save(primary_model, output_modelname)