Куда вставить default если не передаётся фото - JS, mongodb?

const Images = new Schema({ 
kind: { 
        type: String, 
        enum: ['thumbnail', 'detail'], 
        required: false 
    }, 
    url: { 
        type: String 
    }, 
}); 
 
const Tags = new Schema({ 
    label: { 
        type: String 
    }, 
}); 
 
const ArticleScheme = new Schema({ 
    images: [Images], 
    title: {type: String, required: true}, 
    author: {type: String, required: true}, 
    text: {type: String, required: true}, 
    views: { 
        type: Number, 
        default: 123 
    }, 
    tags: [Tags], 
    createdAt: { 
        type: Date 
    } 
});