-It's only occurring with Default state >> Other State transition settings window. For other state transition window, it is working absolutely fine.
-It's working Fine for transition:
Other State >> Default State.
Other State >> Other State
-Workaround: Deselect and select it again the transition settings appears with all the properties.
-Workaround 2: Switch the Inspector into Debug mode.
-Works fine with HDRP template.

Steps to repro:
1. Create a new project > Create a Cube game object.
2. Windows > Animation > Animation > Click on Create button.
3. Project Window > Open Cube Animator > Create Empty State.
4. Create a transition New Animation >> New State.
5. Select transition > Inspector > Expand Settings.

Actual Result:
Animation default transition state property window gets blank.

Expected Result:
Animation default transition state property window should not get blank.

Reproducible in:
2020.2.0a17, 2020.2.0a15.

Working fine in:
2020.2.0a14, 2020.1.0b14.

Environment:
Occurring on Windows 10 & Mac 10.15.