PackageManager option disappears from Window while removing any package and deleting cache at the same time

Steps to Reproduction:

1. Delete Cache from C:\ProgramData\Unity\cache while removing any package
2. Go to Window and Package Manager option disappears.

Note: As PackageManager disappears so the user cannot install or remove packages.

Workaround:
Restart the Unity

Reproducible on: 2018.1.0b13, 2018.1.0b12, 2018.1.0b11, 2018.1.0b5

Note: Package Manager is introduced in 2018.1.0b5

Environment:
Occurring only on:
Windows 10, Windows7