Check NPE and log error condition for enableTransientTaskbar in test harness.

Fixes: 259337908
Bug: 257549303
Test: TaplTestsTaskbar
Change-Id: Ifa929dca18437ae101cf3290feda4209790604d2

quickstep/src/com/android/quickstep/QuickstepTestInformationHandler.java

@@ -1,5 +1,6 @@
 package com.android.quickstep;
 
+import static com.android.launcher3.testing.shared.TestProtocol.NPE_TRANSIENT_TASKBAR;
 import static com.android.launcher3.util.Executors.MAIN_EXECUTOR;
 
 import android.app.Activity;
@@ -7,6 +8,7 @@ import android.content.Context;
 import android.content.res.Resources;
 import android.graphics.Rect;
 import android.os.Bundle;
+import android.util.Log;
 
 import androidx.annotation.Nullable;
 
@@ -184,9 +186,15 @@ public class QuickstepTestInformationHandler extends TestInformationHandler {
 
     private void enableTransientTaskbar(
             TouchInteractionService.TISBinder tisBinder, boolean enable) {
-        // Allow null-pointer to catch illegal states.
         TaskbarActivityContext context = tisBinder.getTaskbarManager().getCurrentActivityContext();
-        DisplayController.INSTANCE.get(context).enableTransientTaskbarForTests(enable);
+        if (context == null) {
+            if (TestProtocol.sDebugTracing) {
+                Log.d(NPE_TRANSIENT_TASKBAR, "enableTransientTaskbar: enable=" + enable,
+                        new Exception());
+            }
+        } else {
+            DisplayController.INSTANCE.get(context).enableTransientTaskbarForTests(enable);
+        }
     }
 
     /**

src/com/android/launcher3/testing/shared/TestProtocol.java

@@ -148,6 +148,7 @@ public final class TestProtocol {
     public static final String MISSING_PROMISE_ICON = "b/202985412";
     public static final String TASKBAR_IN_APP_STATE = "b/227657604";
     public static final String INCORRECT_INFO_UPDATED = "b/239465630";
+    public static final String NPE_TRANSIENT_TASKBAR = "b/257549303";
 
     public static final String REQUEST_EMULATE_DISPLAY = "emulate-display";
     public static final String REQUEST_STOP_EMULATE_DISPLAY = "stop-emulate-display";