First commit weirdness

**Describe the bug**

Using `gitui` to make the first commit in a repository doesn't work, and somehow changes the active branch to `master` (this is not `init.defaultbranch` either, mine is set to `main`)

**To Reproduce**

Steps to reproduce the behavior:
1. Create a blank repository
2. Make a commit
3. Observe that it didn't commit anything
4. Open the `Branches` menu
5. The active branch has changed to `master`
6. `git branch` by now lists only the `master` branch, but it's not active

**Expected behavior**

The commit should have succeeded, and the active branch should not have been changed.

**Screenshots**

Here's an asciinema replay:

https://asciinema.org/a/K8Cu0yDaRTbjROPn9SCwRM6LD

**Context (please complete the following information):**

According to `gitui --bugreport` (env vars and command line omitted):

```
#### Software version

gitui 0.27.0

#### Operating system

- OS: Linux (Fedora Linux 42)
- Kernel: 6.15.8-200.fc42.x86_64

#### Compile time information

- Profile: release
- Target triple: x86_64-unknown-linux-gnu
- Family: unix
- OS: linux
- Architecture: x86_64
- Pointer width: 64
- Endian: little
- CPU features: fxsr,sse,sse2,x87
- Host: x86_64-unknown-linux-gnu
```

**Additional context**
Add any other context about the problem here.