@uppy/aws-s3-multipart file resume cause error - chunk null check is missing

[SimDaeSoo]

Initial checklist

• I understand this is a bug report and questions should be posted in the Community Forum
• I searched issues and couldn’t find anything (or linked relevant results below)

Link to runnable example

https://github.com/SimDaeSoo/UppyResumeErrorSample

Steps to reproduce

i'm using custom express upload server for aws s3 multipart upload.
this is my sample server & react uppy client repository.

https://github.com/SimDaeSoo/UppyResumeErrorSample

1. first run server (yarn start) port = 3001
2. second run react project (yarn start) port = 3000
3. multipart upload
4. !! when some chunk uploaded pause file upload
5. resume
6. error

Expected behavior

There should be no errors and the file should upload successfully.

Actual behavior

file upload resume caused error.

when i'm logging chunks like this code.

some chunk is null like this.
I don't know why some of the chunks are null, but they are.

So I want to modify the code to look like this
Is it okay if I create a PR?

before

uppy/packages/@uppy/aws-s3-multipart/src/index.js

Line 321 in a93e6cd

chunk.setAsUploaded?.()

after

chunk?.setAsUploaded?.()