Initialize colorCircleList earlier to avoid race condition NPE

A race condition on ColorPickerView makes apps crash

How to reproduce

Open the color picker sample
Tap multiple times quickly on Open dialog sampleor Open view sample buttons

It may require many tries to reproduce. I personally had this crash a few times unintentionally.

com.flask.colorpicker.sample E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.flask.colorpicker.sample, PID: 22545
java.lang.NullPointerException: Attempt to invoke interface method 'java.util.Iterator java.util.List.iterator()' on a null object reference
    at com.flask.colorpicker.ColorPickerView.findNearestByPosition(ColorPickerView.java:261)
    at com.flask.colorpicker.ColorPickerView.onTouchEvent(ColorPickerView.java:210)
    at android.view.View.dispatchTouchEvent(View.java:9993)

This PR makes sure the AbsColorWheelRenderer.colorCircleList is never null

QuadFlask / colorpicker

Initialize colorCircleList earlier to avoid race condition NPE #57

How to reproduce