Summary:

Attempting to remove a package using UnityEditor.PackageManager.Client.Remove will return the following error if the project manifest "dependencies" property does not exist:

"Cannot use 'in' operator to search for '<package-name>' in undefined"

Repro steps:
The attached project contains a "DoRemove.cs" script which adds a menu item under "DEBUG -> Remove". This will log an error containing the message from the Package Manager Remove request.

1. Open the attached project in Unity
2. In the menu bar, click "DEBUG" then "Remove"

Expected behaviour:
The Package Manager Client should return an error stating that the package cannot be removed because the dependency does not exist in the project manifest.

Actual behaviour:
The Package Manager Client returns an error stating that the 'in' operator cannot be used.