Tonemapping example image loader not working

## Bevy version 32a5c7db3535250c43738e3da5877497b1274960

Previously, in the tonemapping example an exr or hdr image file could be dragged and dropped onto the window to view the image with the selected tonemapping settings. This no longer works.

The issue was introduced at 35073cf7aa9eaf748e167c103921a6764fcedfb1 with #9885

```
thread 'Compute Task Pool (21)' panicked at 'called `Result::unwrap()` on an `Err` value: InvalidSourceSyntax', crates\bevy_asset\src\path.rs:115:70
```

Reproduce the failure in the tonemapping example with an EXR or HDR drag-and-drop. Start at crates/bevy_asset/src/path.rs:115 and review commit 35073cf7aa9eaf748e167c103921a6764fcedfb1 and #9885 to trace the InvalidSourceSyntax error. Done means both image formats load without a panic and display with the selected tonemapping settings.

Written by the indexing model from the issue text.