Repro steps:(Gif attached)
1) Open attached project and select any sprite in Asset window.
2) In Inspector hit Sprite Editor and edit "Sides" value in upper left - hit change.
- You may need to select sprite in the Sprite Editor after hitting change.
- Notice how "Name" value gets changed in the bottom left corner.

Note: This happens temporarily and won't get saved upon closing the Sprite Editor window

reproduced with: 5.3.4f1, 5.4.0b10