desktop: GitHub Desktop show the wrong default branch

Describe the bug

The default branch for my repo is master. However, GH Desktop shows the default as a different branch, one that is in fact deleted.

Version & OS

GitHub Desktop 2.6.1 MacOS Big Sur, Version 11.1

Steps to reproduce the behavior

1. Go to the remote repo and verify that master is set as the default.
2. Open GitHub Desktop and switch to the local copy of the repo.
3. Click Current Branch to list the branches.
4. See that master is not listed as the default.

Expected behavior

GitHub Desktop should be in synch with the settings of my remote repo.