• Extension version: 0.27.1
• VSCode Version: 1.57.1 (user setup)
• OS: Windows_NT x64 10.0.19043

Steps to Reproduce:

1. Choose an issue
2. click Start Working on Issue and Checkout Topic Branch
3. A prompt pops up to fork
4. Select fork and wait for the fork to complete
5. Choose another issue
6. click Start Working on Issue and Checkout Topic Branch
7. The fork still pops up

This problem occurs when working in a repository from a fork.
I checked the project code and debug log and found that there was a problem with the code, which caused this problem to be repeated.
I fixed the code and submit pr later, please review it.

My native language is not English, please forgive my grammatical error.