当我尝试使用定位小部件封装PandemicCard时，出现以下异常。如果我将卡设置为“单独放置/不放置”窗口小部件，则可以正常工作。
I/flutter ( 7331): ??? EXCEPTION CAUGHT BY RENDERING LIBRARY ??????????????????????????????????????????????????????????
I/flutter ( 7331): The following assertion was thrown during performLayout():
I/flutter ( 7331): RenderStack object was given an infinite size during layout.
I/flutter ( 7331): This probably means that it is a render object that tries to be as big as possible, but it was put
I/flutter ( 7331): inside another render object that allows its children to pick their own size.
I/flutter ( 7331): The nearest ancestor providing …