Input System Package disappears from the list after removing.

Steps to repro:
1. Create a new project.
2. Window > Package Manager > Input System.
3. "preview.3 - 1.0.0" package > Install.
4. Remove Input System package.

Actual Result:
Input System Package disappears from the list.

Expected Result:
Input System Package should not be disappeared from the list.

Tested with Unity Version: 2020.1.0a13, 2020.1.0a11.

Working fine with Unity Version:2020.1.0a10, 2019.3.0b11.

Reproducible in Package Version: preview.3 - 1.0.0.

NOTE: Working fine with preview.2 - 1.0.0 in Unity 2019.3.0b11(preview.3 is not available).

Environment:
Windows 10 & Mac 10.14.