ActivityManagerInternal null check while checking process state

Bug: 390107600
Test: atest DisplayManagerServiceTest
Flag: com.android.server.display.feature.flags.refresh_rate_event_for_foreground_apps
Change-Id: I2977e221ad342a026c915f5869e825ed102925be
diff --git a/services/core/java/com/android/server/display/DisplayManagerService.java b/services/core/java/com/android/server/display/DisplayManagerService.java
index 3598b9b..a11dd3b 100644
--- a/services/core/java/com/android/server/display/DisplayManagerService.java
+++ b/services/core/java/com/android/server/display/DisplayManagerService.java
@@ -4157,7 +4157,8 @@
 
         public boolean shouldReceiveRefreshRateWithChangeUpdate(int event) {
             if (mFlags.isRefreshRateEventForForegroundAppsEnabled()
-                    && event == DisplayManagerGlobal.EVENT_DISPLAY_REFRESH_RATE_CHANGED) {
+                    && event == DisplayManagerGlobal.EVENT_DISPLAY_REFRESH_RATE_CHANGED
+                    && mActivityManagerInternal != null) {
                 int procState = mActivityManagerInternal.getUidProcessState(mUid);
                 int importance = ActivityManager.RunningAppProcessInfo
                         .procStateToImportance(procState);
diff --git a/services/tests/displayservicetests/src/com/android/server/display/DisplayManagerServiceTest.java b/services/tests/displayservicetests/src/com/android/server/display/DisplayManagerServiceTest.java
index e8b28ac..b5ea0df 100644
--- a/services/tests/displayservicetests/src/com/android/server/display/DisplayManagerServiceTest.java
+++ b/services/tests/displayservicetests/src/com/android/server/display/DisplayManagerServiceTest.java
@@ -2126,11 +2126,12 @@
 
     @Test
     public void test_displayChangedNotified_displayInfoFramerateOverridden() {
+        when(mMockFlags.isFramerateOverrideTriggersRrCallbacksEnabled()).thenReturn(false);
+
         DisplayManagerService displayManager =
-                new DisplayManagerService(mContext, mShortMockedInjector);
+                new DisplayManagerService(mContext, mBasicInjector);
         DisplayManagerService.BinderService displayManagerBinderService =
                 displayManager.new BinderService();
-        when(mMockFlags.isFramerateOverrideTriggersRrCallbacksEnabled()).thenReturn(false);
 
         registerDefaultDisplays(displayManager);
         displayManager.onBootPhase(SystemService.PHASE_WAIT_FOR_DEFAULT_DISPLAY);