Bevy fails to use any fallback audio driver when ALSA compatibility is not present.

## Bevy version and features
v0.17.3 on crates.io

## Relevant system information
I am using Pipewire for audio system.
`pipewire-alsa` is *not* installed (meaning that apps that rely on only ALSA will not have any available audio back-end)

## What you did

`cargo run` on default bevy_audio settings + wav

## What went wrong

I didnt hear anything, and no error/warning was logged.

Fallback to pulse audio, or a warning being shown.

## Additional information

```
an error occurred on output stream: A backend-specific error has occurred: ALSA function 'snd_pcm_poll_descriptors' failed with error 'Unknown errno (-32)'
```

Looks like bevy thinks it is playing music (due to the presence of AudioSink)

Related: https://github.com/bevyengine/bevy/issues/2705

Start by reproducing the issue with `cargo run` using default `bevy_audio` settings and a WAV file on a system without `pipewire-alsa`. Trace the audio backend error shown in the report and determine whether the completed change should select a fallback backend or emit a warning when no usable backend is available.

Written by the indexing model from the issue text.