NullReferenceException error is thrown on selecting AdaptivePerformanceGeneralSettings preset asset after deleting AdaptivePerformanceGeneralSettings asset.

Steps to repro:
1. Create a new project.
2. Edit > Project Settings > Adaptive Performance > Install.
3. Project Winodw > Select AdaptivePerformanceGeneralSettings > create its Preset.
4. Project Window > Delete AdaptivePerformanceGeneralSettings.
5. Select AdaptivePerformanceGeneralSettings preset asset.

Actual Result:
NullReferenceException is thrown in the console.

Expected Result:
No error in the console.

Reproducible in:
2020.2.0a15, 2020.1.0b13, 2020.1.0a11 with Package Version 2.0.0-preview.8.

Note: Adaptive Performance and simulator option is not available in Project settings with Package Version 2.0.0-preview.4.

Environment:
Occurring on Windows 10 & Mac 10.15.

Stacktrace:
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.AdaptivePerformance.Editor.AdaptivePerformanceGeneralSettingsPerBuildTarget.OnEnable () (at library/packagecache/com.unity.adaptiveperformance@2.0.0-preview.8/editor/management/adaptiveperformancegeneralsettingsperbuildtarget.cs:38)
UnityEditor.Presets.PresetEditor:OnEnable()