No author information was supplied by the version control system

You can set the author information using Terminal. It might be possible that xCode has the author data but it's not actually set in Git config.

Setting your Git username for every repository on your computer

1) Open Terminal.

2) Set a Git username:

$ git config --global user.name "Mona Lisa"

3) Confirm that you have set the Git username correctly:

$ git config --global user.name> Mona Lisa

Setting your Git username for a single repository

1) Open Terminal.

2) Change the current working directory to the local repository where you want to configure the name that is associated with your Git commits.

3) Set a Git username:

$ git config user.name "Mona Lisa"

4) Confirm that you have set the Git username correctly:

$ git config user.name> Mona Lisa

Source: https://help.github.com/en/articles/setting-your-username-in-git

Click on "Fix" and provide your Git username and email. This fixed my issue.

Just click Fix and enter your customized Author Name & Author Email to fix the problem.

But if you accidentally press Cancel and forget to fix the problem, can we still develop an iOS App?

In fact, it is possible, but there will be problems when we are doing version management and committing. Therefore, in order for the project to be successfully committed, we need to open the Preferences window of Xcode, switch to the Source Control tab, and enter Author Name & Author Email on the Git page.

And go to a git tag and fill the information as above image