If you remove a RenderBox whose parent used its baseline, we'll throw later

1. Run Stocks in checked mode
2. Drawer > Settings
3. Enable "show baselines" mode
4. Back
5. Drawer

or:
1. Run Stocks in checked mode
2. Drawer > Settings
3. Enable "show baselines" mode
4. Toggle material grid on and off.

The problem is RenderBox.markNeedsLayout() doesn't check if it has a parent. The actual fix is probably just `parent.markNeedsLayout();` -> `parent?.markNeedsLayout();`.
