In Terrain, when paint texture is selected, deleting the Terrain component and again adding Terrain component to Terrain game object, NullReference Exception thrown on assigning Terrain data asset to the newly added terrain component.

Steps to repro:
1. Create a new project.
2. Hierarchy > 3D object > Terrain > Inspector > Paint Terrain > Paint Texture.
3. Remove the Terrain component.
4. Hierarchy > Terrain > Add Component > Terrain
4. Assign Terrain data asset to the Terrain component.
5. Observe the errors in the console.

Actual Result:
NullReference exceptions thrown

Expected Result:
No errors in the console

Reproducible in:
2020.2.0a20, 2020.1.2f1, 2019.4.7f1, 2019.3.16f1, 2019.3.0a5

Working Fine in:
2019.3.0a4, 2018.4.26f1

Environment:
Windows 10 & macOS 10.14

Stack Trace:
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.Experimental.TerrainAPI.PaintTextureTool.OnInspectorGUI (UnityEngine.Terrain terrain, UnityEditor.Experimental.TerrainAPI.IOnInspectorGUI editContext) (at <70c42c992fa442f8aa9edcf3e9f7b431>:0)
UnityEditor.TerrainInspector.ShowPaint () (at <70c42c992fa442f8aa9edcf3e9f7b431>:0)
UnityEditor.TerrainInspector.OnInspectorGUI () (at <70c42c992fa442f8aa9edcf3e9f7b431>:0)
UnityEditor.UIElements.InspectorElement+<>c__DisplayClass58_0.<CreateIMGUIInspectorFromEditor>b__0 () (at <4a010c27075a4c2daedf3ee971af3236>:0)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr, Boolean&)