New warning: ``‘fmt’ may be used uninitialized in this function [-Wmaybe-uninitialized]``

# Bug report

### Bug description:

Popped up in https://github.com/python/cpython/pull/116101/files and https://github.com/python/cpython/pull/116096/files

### CPython versions tested on:

CPython main branch

### Operating systems tested on:

_No response_


### Linked PRs
* gh-116230