Corners appear black when using border radius for icon and overlay with opacity

[VijayMeenaRI]

SpeedDial(
buttonSize: Size(50.0, 50),
backgroundColor: Colors.blue,
curve: Curves.bounceInOut,
overlayColor: Colors.black,
overlayOpacity: 0.4,
shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(8.5.r)),
icon: Icons.add,
activeIcon: Icons.close,
elevation: 0,
spacing: 13,
animationDuration: Duration(milliseconds: 5),
iconTheme: IconThemeData(color: Colors.white, size: 32),
children: [
SpeedDialChild(
labelWidget: Container(
height: 35.h,
alignment: Alignment.center,
padding: EdgeInsets.symmetric(horizontal: 14.w, vertical: 7.h),
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(7), color: Colors.blue),
child: CustomText(text: 'Add', fontStyle: FontStyle.C5),
),
onTap: () => print('Add')),
SpeedDialChild(
labelWidget: Container(
height: 35.h,
alignment: Alignment.center,
padding: EdgeInsets.symmetric(horizontal: 14.w, vertical: 7.h),
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(7), color: Colors.blue),
child: CustomText(text: 'Edit', fontStyle: FontStyle.C5),
),
onTap: () => print('Edit')),
SpeedDialChild(
labelWidget: Container(
height: 35.h,
alignment: Alignment.center,
padding: EdgeInsets.symmetric(horizontal: 14.w, vertical: 7.h),
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(7), color: Colors.blue),
child: CustomText(text: 'Delete', fontStyle: FontStyle.C5),
),
onTap: () => print('Delete')),
],
)