buildBackPanelPortrait method Null safety

Implementation

@override
Widget buildBackPanelPortrait(
        BuildContext context, final ScreenPositioner screen) =>
    Stack(fit: StackFit.expand, children: [
      Container(color: MainScreen.keyboardBaseColor),
      screen.box(Rect.fromLTWH(screen.width - 0.8, 0.0, 0.8, 0.8),
          const Icon(Icons.arrow_back, color: Colors.white)),
      screen.box(
          const Rect.fromLTWH(0.1, 0.1, 5.03 * 0.57, 1.98 * 0.57),
          Image.asset(
              'packages/jrpn/assets/NAFO_OFAN_brain_damaged_cartoon_dogs.jpeg')),
      screen.box(const Rect.fromLTWH(0.78, 3.6, .75, 3), tryzub(1)),
      screen.box(const Rect.fromLTWH(0.4, 7.23, 1.6, 2.2), sigmaTable(1.6)),
      screen.box(const Rect.fromLTWH(2.52, 3.27, 5, 3.4), drawingTable(5)),
      ...jumpTableList(screen, 3.70, 0.2),
      screen.box(const Rect.fromLTWH(0.2, 1.57, 3.5, 2.2), metricTable(3.5)),
      screen.box(const Rect.fromLTWH(2.10, 7.20, 4, 5), numberTable(4.0))
    ]);