IndexOutOfRangeException error is thrown on creating animation parameter.

Steps to repro:
1. Create a new project.
2. Gameobject > 3D Object > Cube.
3. Select Cube > Windows > Animation > Create.
4. Project Window > Open Cube Animator > Click on the Parameter tab.
5. Click on "+" > Float.

Actual Result:
IndexOutOfRangeException error is thrown in the console.

Expected Result:
No error in the console.

Reproducible in:
2021.1.0a2, 2021.1.0a1.

Working Fine in:
2020.2.0b8, 2020.1.10f1.

Environment:
Occurring on Windows 10 & Mac 10.15.

Stacktrace:
IndexOutOfRangeException: Index was outside the bounds of the array.
UnityEditor.Graphs.ParameterControllerView.AddParameterMenu (System.Object value) (at <492b4e7aa2b24ec0abeac998d966f035>:0)
UnityEditor.GenericMenu.CatchMenu (System.Object userData, System.String[] options, System.Int32 selected) (at <193ca33d21dd486998e80992690939b0>:0)