GUI error occurs on adding rigidbody 2D component on a game object and no further components can be added to that game object

Steps to Repro:
1. Create a new or open attached project
2. Hierarchy > right click
3. Create an empty game object
4. Add component > rigidbody 2D

Actual Result:
1. Observe that the console is spammed with warnings and errors, also notice a horizontal black line coming next to 'Rigidbody' properties
2. Add component button disappears from the inspector
3. Further components are getting added to the game object

Environment:
Windows and Mac

Occurring with:
Version 2018.3.0a2 (e9113db2e9bf)
Branch: prefabs/improved

Working with:
Version 2018.3.0a3 (0ac1bca97520)
Branch: trunk

Version 2018.3.0a2 (7fc052e81176)
Branch: trunk

Stack Trace:
Warning:
Unexpected top level layout group! Missing GUILayout.EndScrollView/EndVertical/EndHorizontal?
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

Error:
GUI Error: You are pushing more GUIClips than you are popping. Make sure they are balanced)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)