Error when using projectile to enter `.emacs.d`

Having Mindstream anonymous sessions in the `.emacs.d` folder (i.e. the current default, at `.emacs.d/mindstream/anon`) and attempting to enter this folder via `projectile-switch-project` results in errors like this:

```
fatal: no submodule mapping found in .gitmodules for path 'mindstream/anon/2024-04-17-4b9b3454daf5e680300e8375ea77b00d66a60fd4'
...
```

**Workaround**: Set `mindstream-path` to something outside the `.emacs.d` folder. See [Choosing a Session Path](https://github.com/countvajhula/mindstream?tab=readme-ov-file#choosing-a-session-path) for how to do this.