How to reproduce:
1. Open the attached 'project-1182627.zip' project
2. In the Project window select 'Square'
3. In the Inspector window open Sprite Editor
4. In the Sprite Editor change editor's mode to 'Skinning Editor'
5. Enable the 'Visibility' tool and observe it

Expected result: reset button ('x') is not visible (as nothing is entered into the search field)
Actual result: reset button ('x') is visible

Reproducible with: 2018.4.10f1 (2.0.0), 2019.2.7f2 (2.2.0), 2019.3.0b5, 2020.1.0a5 (3.0.5)
Could not test with: 2017.4.32f1 (Skinning Editor not available)

Note: clicking on the 'x' button will make it disappear until something is entered into the search field