NullPointerException in onDraw() once alpha channel enabled

[riggaroo]

Hi there 👋 Thanks for a great library 🥇 We've been using it pretty successfully without any issues for a while. Recently, I enabled the alpha slider in XML via app:cpv_alphaChannelVisible="true", but now we are experiencing a crash with the onDraw function.

Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.graphics.Rect.width()' on a null object reference
       at com.jaredrummler.android.colorpicker.ColorPickerView.onDraw(ColorPickerView.java:265)
       at android.view.View.draw(View.java:23191)
       at android.view.View.updateDisplayListIfDirty(View.java:22066)
       at android.view.View.draw(View.java:22921)
       at android.view.ViewGroup.drawChild(ViewGroup.java:5230)
       at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4987)
       at androidx.constraintlayout.widget.ConstraintLayout.dispatchDraw(ConstraintLayout.java:1882)
       at android.view.View.draw(View.java:23194)
       at android.view.View.updateDisplayListIfDirty(View.java:22066)
       at android.view.View.draw(View.java:22921)
       at android.view.ViewGroup.drawChild(ViewGroup.java:5230)
       at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4987)
       at androidx.constraintlayout.widget.ConstraintLayout.dispatchDraw(ConstraintLayout.java:1882)
       at androidx.constraintlayout.motion.widget.MotionLayout.dispatchDraw(MotionLayout.java:2885)