Fix NPE in DialogLaunchAnimator

This CL fixes a NPE happening in DialogLaunchAnimator if it tried to
synchronize the 2 view roots at the start/end of the animation and that
the view that triggered the animation was detached from the hierarchy.
This regression was caused by the refactoring in http://ag/20139844.

Bug: 256194999
Test: Manual
Change-Id: Id264ddfa6365bfdc952d512c2c182b6cbf4906e4

packages/SystemUI/animation/src/com/android/systemui/animation/DialogLaunchAnimator.kt

@@ -75,7 +75,7 @@ constructor(
      */
     interface Controller {
         /** The [ViewRootImpl] of this controller. */
-        val viewRoot: ViewRootImpl
+        val viewRoot: ViewRootImpl?
 
         /**
          * The identity object of the source animated by this controller. This animator will ensure
@@ -807,15 +807,17 @@ private class AnimatedDialog(
      * inversely, removed from the overlay when the source is moved back to its original position).
      */
     private fun synchronizeNextDraw(then: () -> Unit) {
-        if (forceDisableSynchronization) {
-            // Don't synchronize when inside an automated test.
+        val controllerRootView = controller.viewRoot?.view
+        if (forceDisableSynchronization || controllerRootView == null) {
+            // Don't synchronize when inside an automated test or if the controller root view is
+            // detached.
             then()
             return
         }
 
-        ViewRootSync.synchronizeNextDraw(controller.viewRoot.view, decorView, then)
+        ViewRootSync.synchronizeNextDraw(controllerRootView, decorView, then)
         decorView.invalidate()
-        controller.viewRoot.view.invalidate()
+        controllerRootView.invalidate()
     }
 
     private fun findFirstViewGroupWithBackground(view: View): ViewGroup? {

packages/SystemUI/animation/src/com/android/systemui/animation/ViewDialogLaunchAnimatorController.kt

@@ -28,7 +28,7 @@ internal constructor(
     private val source: View,
     override val cuj: DialogCuj?,
 ) : DialogLaunchAnimator.Controller {
-    override val viewRoot: ViewRootImpl
+    override val viewRoot: ViewRootImpl?
         get() = source.viewRootImpl
 
     override val sourceIdentity: Any = source

packages/SystemUI/compose/core/src/com/android/systemui/compose/animation/ExpandableController.kt

@@ -262,7 +262,7 @@ internal class ExpandableControllerImpl(
 
     private fun dialogController(cuj: DialogCuj?): DialogLaunchAnimator.Controller {
         return object : DialogLaunchAnimator.Controller {
-            override val viewRoot: ViewRootImpl = composeViewRoot.viewRootImpl
+            override val viewRoot: ViewRootImpl? = composeViewRoot.viewRootImpl
             override val sourceIdentity: Any = this@ExpandableControllerImpl
             override val cuj: DialogCuj? = cuj