How to reproduce:
1. Open attached project (or add Mobile Notifications package to new project)
2. Go to Project settings and open Mobile Notifications pane
3. Under Android, click + sign to add notification icon
4. Open Build settings and build any platform
5. In Mobile Notifications pane click - sign, then +
6. Observe Console

Expected result: Icon is deleted successfully and then can be added back
Actual result: + or - buttons throwing errors and icon list is blank

Reproducible with: 1.4.2-1.3.0 (2019.4.31f1, 2020.3.19f1, 2021.1.22f1, 2021.2.0b14, 2022.1.0a10)
Not reproducible with: 1.0.3 (2019.4.31f1, 2020.3.19f1, 2021.1.22f1, 2021.2.0b14, 2022.1.0a10)

Note: Closing Project settings window and reopening fixes the issue

Errors:
ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
System.ThrowHelper.ThrowArgumentOutOfRangeException (System.ExceptionArgument argument, System.ExceptionResource resource) (at <eae584ce26bc40229c1b1aa476bfa589>:0)

ArgumentNullException: Value cannot be null.
Parameter name: identifier
UnityEditor.Undo.RegisterCompleteObjectUndo (UnityEngine.Object objectToUndo, System.String name) (at /Users/bokken/buildslave/unity/build/Editor/Mono/Undo/Undo.bindings.cs:49)
Unity.Notifications.NotificationSettingsProvider.<InitReorderableList>b__19_0 (UnityEditorInternal.ReorderableList list) (at Library/PackageCache/com.unity.mobile.notifications@1.4.2/Editor/NotificationSettingsProvider.cs:85)
UnityEditorInternal.ReorderableList+Defaults.DrawFooter (UnityEngine.Rect rect, UnityEditorInternal.ReorderableList list) (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/ReorderableList.cs:118)
UnityEditorInternal.ReorderableList.DoListFooter (UnityEngine.Rect footerRect) (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/ReorderableList.cs:660)
UnityEditorInternal.ReorderableList.DoList (UnityEngine.Rect rect) (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/ReorderableList.cs:427)
Unity.Notifications.NotificationSettingsProvider.OnGUI (System.String searchContext) (at Library/PackageCache/com.unity.mobile.notifications@1.4.2/Editor/NotificationSettingsProvider.cs:256)
UnityEditor.SettingsWindow.DrawControls () (at /Users/bokken/buildslave/unity/build/Editor/Mono/Settings/SettingsWindow.cs:389)
UnityEditor.SettingsWindow.DrawSettingsPanel () (at /Users/bokken/buildslave/unity/build/Editor/Mono/Settings/SettingsWindow.cs:367)
UnityEngine.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 parentTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout, UnityEngine.Rect layoutSize, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:293)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:508)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/buildslave/unity/build/