NullReferenceException when adding SoftMask component

[CDTR-MattConroy]

Describe the bug
When adding a SoftMask component to an empty GameObject, NullReferenceExceptions are continuously thrown until a Graphic is also added.

To Reproduce
Steps to reproduce the behavior:

1. Create an empty GameObject
2. Add a SoftMask component
3. See error in console

Expected behavior
No errors are thrown when adding a SoftMask component.
Either a default Graphic should be added if required (during Reset or OnValidate), or ideally, handle missing Graphic components.

Environment (please complete the following information):

• Version: 1.0.2
• Platform: Editor(Windows)
• Unity version: 2022.3.9f1

Additional context

NullReferenceException: Object reference not set to an instance of an object
Coffee.UISoftMask.SoftMask.UpdateMaskTextures () (at ./Library/PackageCache/com.coffee.softmask-for-ugui@1.0.2/Scripts/SoftMask.cs:476)
UnityEngine.Canvas.SendWillRenderCanvases () (at <836aea33117647b388cc5f48bed669c4>:0)