组件的属性是否可以传递Undifined

@Entry 
@Component 
struct Index { 
  @State needSetColor: Boolean = false 
  @State needSetSize: Boolean = false 
  build() { 
    Row() { 
      Column() { 
        Text('hello') 
          .fontSize(this.needSetSize ? 30 : undefined) 
          .textAlign(TextAlign.Center) 
          .fontColor(this.needSetColor ? '#ff9b1919' : undefined) 
 
        Text('hello') 
          .textAlign(TextAlign.Center) 
      } 
      .width('100%') 
    } 
    .height('100%') 
 
  } 
}