Sprites do not work with images after get_mut

## Bevy version

0.15

## What you did

I used `Assets::get_mut` to get a mutable reference to an image.

## What went wrong

I expected the resized image to be rendered to the screen. Instead, the image just disappears and doesn't get rendered to the screen.

## Additional information

This might be happening because the asset is being flagged as `Modified` when you get a mutable reference to it and the one of the sprite systems removes all images that are flagged as `Modified`.

Reproduce the issue in Bevy 0.15 by mutating an image through Assets::get_mut and observing sprite rendering. Trace how modified image assets are handled by the sprite systems; done means a resized image obtained this way remains rendered on screen.

Written by the indexing model from the issue text.