fl_chart crashed if all the value are negative in bar chart

**Describe the bug**
fl_chart crashed if all the value are negative in bar chart

**To Reproduce**
Input all negative values in a bar chart

**Versions**
- which version of the Flutter are you using? 3.24.1
- which version of the FlChart are you using? 0.68.0

Reproduce the crash by creating a bar chart with only negative values using Flutter 3.24.1 and fl_chart 0.68.0. Start at the bar chart entry point and trace the failure, then add a regression test covering all-negative data. Done means the chart renders without crashing for that input.

Written by the indexing model from the issue text.