bug: animate can cause wrong state

[EinfachHans]

Description

First: I really like this package. Thank you for that awesome work! Today i experienced two bug:

Bug 1

First one is easy explained. With a value of 0 and a max value > 0, you still see a little bit filled:

This is also easily reproduceable through the live demo on your docs page.

Bug 2

The second bug is a little bit trickier. From my debugging: It seems that if animate is set to true in a special case you can have this outcome with min: 0, max: 2 and value: 0:

Steps to reproduce:

1. min: 0, max: 3 and value: 1
2. Update value to 0 (_oldChangeVal will be 1)
3. Then update max to 2

When animate is false this does not happen. I guess somehow the _oldChangeVal is the problem)