set function causes an uncaught promise error.

Hi there.
I am using this line:
```
bar.set(0);
```
I am having problem in handling this. kindly help as I am not having much knowledge of javascript.
Thank you.

Start by reproducing the reported bar.set(0) call in a minimal progressbar.js example and capture the uncaught promise error. Then trace the set entry point to determine the expected handling; done means the call no longer produces an uncaught promise error, with behavior confirmed by a regression check.

Written by the indexing model from the issue text.