Failed assertion: line 24 pos 15: 'color != null && color.alpha == 0xFF': is not true

flutter报错Failed assertion: line 24 pos 15: 'color != null && color.alpha == 0xFF': is not true

原因是

theme: ThemeData(
    primaryColor: Color.fromRGBO(12, 23, 23, 0.8), // 用这个我会报错，我改成Colors.blue就不报错了

 　　primarySwatch: Colors.blue, 
),

参考文章：https://stackoverflow.com/questions/61813780/failed-assertion-line-24-pos-15-color-null-color-alpha-0xff-is-not