lineChart.clear() and lineChart.clearAll() do not work

[nelsaow]

I'm trying to clean de view and get an error, fatal error: unexpectedly found nil while unwrapping an Optional value. How can I use lineChart.clear()?

[anakayub]

This is how I implemented lineChart.clearAll() (as part of pickerView(_:didSelectRow:inComponent:)):
self.lineChart.clearAll() self.lineChart.removeFromSuperview() viewModel.liftPickerDidSelectRow(row: row, inComponent: component) drawLineChart()