Delete button functionality not working for blend tree motion property and transition condition property

Steps to Repro:
1. Open attached project > Project window > select animator controller
2. Animator window > select blend transition from blend tree to new state
3. Select any condition > hit delete button > observe the condition doesn't get deleted
4. Double click blend tree and select it > select any motion property
5. Hit delete button > observe the condition doesn't get deleted

Expected Result:
transition conditions and motion properties should get deleted when hitting the delete button

Occurring with:
2018.1.0b5, 2017.3.0p4, 2017.2.1p2, 2017.1.3f1, 5.6.5p1

Workaround:
condition and motion property can be deleted using negative button inside inspector window for transition and blend tree

Environment:
Occurring on windows and Mac