Animation Freezing

**Describe the bug**
It seems like after enough points are added the animation will freeze, however, moving my finger along the graph constantly lets the animation unfreeze and continue normally. Video attached.

(To be clear the animation works fine for the first few points - I am not moving my finger during the first few seconds of the video)

**To Reproduce**
https://gist.github.com/ByrdOfAFeather/d95fa056ba188c22d7ef4065e4968bb8

**Screenshots**
https://www.youtube.com/watch?v=_ZnGTPEuNb0

**Versions**
Flutter version: 1.21
FLChart: ^0.11.1

Start with the linked reproduction gist using Flutter 1.21 and FLChart ^0.11.1, then observe whether the animation freezes after enough points without finger movement. The issue names no source file or test; done means the reproduced animation continues normally and the regression is covered by verification or a test.

Written by the indexing model from the issue text.