Animation on bar chart appears sometimes.

Animation on bar chart appears sometimes. Usually the data changes suddenly like a flash and the animation works only sometimes. It is when changing for example year for the stats.

**Versions**
- which version of the Flutter are you using? Newest available.
- which version of the FlChart are you using? Newest available.

The issue names no files, tests, or reproducible example. Start by reproducing the bar-chart update while changing the year with the newest Flutter and FL Chart versions, then locate the bar-chart animation entry point and add a regression test or example showing that the transition runs consistently.

Written by the indexing model from the issue text.