fix: prevent crash when there is no appearance model built (#2375)

## Description

I haven't investigated it carefully, but there were case when updating
`sheetCornerRadius` the appearance
model has not been built yet leading to a crash when casting to a
non-null type.

Additionally, this PR prevents calls to `onSheetCornerRadiusUpdate` when
not in `formSheet` presentation
or not in native stack.

## Changes

* Prevent calls to `onSheetCornerRadiusUpdate` when not in `formSheet`
presentation.
* Check for nullish view background before attempt to set the corner
radius.
* Update the corner radius after all updates are applied, so that the
`stackPresentation` has change of being updated.

## Test code and steps to reproduce

`Test1649`. Try setting the corner radius now, should work properly.

## Checklist

- [x] Included code example that can be used to test this change
- [ ] Ensured that CI passes

android/src/main/java/com/swmansion/rnscreens/Screen.kt

@@ -21,6 +21,9 @@ import com.facebook.react.uimanager.UIManagerModule
 import com.facebook.react.uimanager.events.EventDispatcher
 import com.facebook.react.views.scroll.ReactScrollView
 import com.google.android.material.bottomsheet.BottomSheetBehavior
+import com.google.android.material.shape.CornerFamily
+import com.google.android.material.shape.MaterialShapeDrawable
+import com.google.android.material.shape.ShapeAppearanceModel
 import com.swmansion.rnscreens.events.HeaderHeightChangeEvent
 import com.swmansion.rnscreens.events.SheetDetentChangedEvent
 
@@ -54,10 +57,16 @@ class Screen(
 
     // Props for controlling modal presentation
     var isSheetGrabberVisible: Boolean = false
+
+    // corner radius must be updated after all props prop updates from a single transaction
+    // have been applied, because it depends on the presentation type.
+    private var shouldUpdateSheetCornerRadius = false
     var sheetCornerRadius: Float = 0F
         set(value) {
-            field = value
-            (fragment as? ScreenStackFragment)?.onSheetCornerRadiusChange()
+            if (field != value) {
+                field = value
+                shouldUpdateSheetCornerRadius = true
+            }
         }
     var sheetExpandsWhenScrolledToEdge: Boolean = true
 
@@ -420,6 +429,28 @@ class Screen(
         )
     }
 
+    internal fun onFinalizePropsUpdate() {
+        if (shouldUpdateSheetCornerRadius) {
+            shouldUpdateSheetCornerRadius = false
+            onSheetCornerRadiusChange()
+        }
+    }
+
+    internal fun onSheetCornerRadiusChange() {
+        if (stackPresentation !== StackPresentation.FORM_SHEET || background == null) {
+            return
+        }
+        (background as MaterialShapeDrawable?)?.let {
+            it.shapeAppearanceModel =
+                ShapeAppearanceModel
+                    .Builder()
+                    .apply {
+                        setTopLeftCorner(CornerFamily.ROUNDED, sheetCornerRadius)
+                        setTopRightCorner(CornerFamily.ROUNDED, sheetCornerRadius)
+                    }.build()
+        }
+    }
+
     enum class StackPresentation {
         PUSH,
         MODAL,

android/src/main/java/com/swmansion/rnscreens/ScreenStackFragment.kt

@@ -198,13 +198,7 @@ class ScreenStackFragment :
     }
 
     internal fun onSheetCornerRadiusChange() {
-        (screen.background as MaterialShapeDrawable).shapeAppearanceModel =
-            ShapeAppearanceModel
-                .Builder()
-                .apply {
-                    setTopLeftCorner(CornerFamily.ROUNDED, screen.sheetCornerRadius)
-                    setTopRightCorner(CornerFamily.ROUNDED, screen.sheetCornerRadius)
-                }.build()
+        screen.onSheetCornerRadiusChange()
     }
 
     override fun onCreateView(

android/src/main/java/com/swmansion/rnscreens/ScreenViewManager.kt

@@ -92,6 +92,12 @@ open class ScreenViewManager :
         return super.updateState(view, props, stateWrapper)
     }
 
+    // Called after all props are updated for given view
+    override fun onAfterUpdateTransaction(view: Screen) {
+        super.onAfterUpdateTransaction(view)
+        view.onFinalizePropsUpdate()
+    }
+
     @ReactProp(name = "activityState")
     fun setActivityState(
         view: Screen,