NPE crash when navigating back from ReactNativeActivity to Native activity.

[floynn-shopify]

Steps to reproduce:

1. Checkout https://github.com/Shopify/mobile/tree/segment_list_prototype_with_flash_list
2. Run the android app.
3. Navigate to Store tab.
4. Swipe debug menu from the right side of the screen and enable Feature Flags -> CustomerSegmentListRN.
5. Click Customers. You should be able to see your segment list implemented via FlashList
6. Click <- arrow in the upper right corner to navigate back and observe the crash.

Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'android.view.ViewParent android.view.ViewParent.getParent()' on a null object reference
        at com.shopify.reactnative.flash_list.AutoLayoutView.dispatchDraw(AutoLayoutView.kt:33)
        at android.view.View.updateDisplayListIfDirty(View.java:21510)
        at android.view.View.draw(View.java:22375)
        at android.view.ViewGroup.drawChild(ViewGroup.java:4528)
        at com.facebook.react.views.view.ReactViewGroup.drawChild(ReactViewGroup.java:772)
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4313)
        at com.facebook.react.views.view.ReactViewGroup.dispatchDraw(ReactViewGroup.java:744)
        	... 95 more

It looks like it's happening here

flash-list/android/src/main/kotlin/com/shopify/reactnative/flash_list/AutoLayoutView.kt

Line 33 in 482c5b4

val scrollContainerSize = (parent.parent as View).let {

due to parent view being null at this point.