Add extra `None` option for VAE

    AxisOption("Denoising", float, apply_field("denoising_strength")),

    AxisOptionTxt2Img("Hires upscaler", str, apply_field("hr_upscaler"), choices=lambda: [*shared.latent_upscale_modes, *[x.name for x in shared.sd_upscalers]]),

    AxisOptionImg2Img("Cond. Image Mask Weight", float, apply_field("inpainting_mask_weight")),

    AxisOption("VAE", str, apply_vae, cost=0.7, choices=lambda: list(sd_vae.vae_dict)),

    AxisOption("VAE", str, apply_vae, cost=0.7, choices=lambda: ['None'] + list(sd_vae.vae_dict)),

    AxisOption("Styles", str, apply_styles, choices=lambda: list(shared.prompt_styles.styles)),

    AxisOption("UniPC Order", int, apply_uni_pc_order, cost=0.5),

    AxisOption("Face restore", str, apply_face_restore, format_value=format_value),