Call back with null AssistContent if request fails

Ensures that the onAssistContent method is always called (with null if
necessary).

Bug: 341017571
Fix: 341017571
Test: manual via checking that the callback in the
ScreenshotActionsProvider is called
Flag: com.android.systemui.screenshot_shelf_ui2

Change-Id: I762e6fe96c24f4b60fcb15285c38873faf166d91

packages/SystemUI/src/com/android/systemui/screenshot/AssistContentRequester.java

diff --git a/packages/SystemUI/src/com/android/systemui/screenshot/AssistContentRequester.java b/packages/SystemUI/src/com/android/systemui/screenshot/AssistContentRequester.java
index 12bff49..6ff1535 100644
--- a/packages/SystemUI/src/com/android/systemui/screenshot/AssistContentRequester.java
+++ b/packages/SystemUI/src/com/android/systemui/screenshot/AssistContentRequester.java
@@ -89,9 +89,12 @@
         // ActivityTaskManager interaction here is synchronous, so call off the main thread.
         mSystemInteractionExecutor.execute(() -> {
             try {
-                mActivityTaskManager.requestAssistDataForTask(
+                boolean success = mActivityTaskManager.requestAssistDataForTask(
                         new AssistDataReceiver(callback, this), taskId, mPackageName,
                         mAttributionTag);
+                if (!success) {
+                    callback.onAssistContentAvailable(null);
+                }
             } catch (RemoteException e) {
                 Log.e(TAG, "Requesting assist content failed for task: " + taskId, e);
             }