Perform null check before updating originating tokens

Turns out it's possible that when the callback is processed there is no
process attached to the ServiceRecord despite it being allowed for bg
activity starts "by start". This can happen for example if we call
allowBgActivityStartsOnServiceStart() twice without a process attached.

This was handled before ag/12559801, so also needs to be handled in the
new code-path.

Bug: 176813978
Test: atest BackgroundActivityLaunchTest
Change-Id: I2024f5cb4da78a93c868a63e45c00567c20848ba

services/core/java/com/android/server/am/ServiceRecord.java

@@ -749,9 +749,15 @@ final class ServiceRecord extends Binder implements ComponentName.WithComponentN
                         // There are other callbacks in the queue, let's just update the originating
                         // token
                         if (mIsAllowedBgActivityStartsByStart) {
-                            mAppForAllowingBgActivityStartsByStart
-                                    .addOrUpdateAllowBackgroundActivityStartsToken(
-                                            this, getExclusiveOriginatingToken());
+                            // mAppForAllowingBgActivityStartsByStart can be null here for example
+                            // if get 2 calls to allowBgActivityStartsOnServiceStart() without a
+                            // process attached to this ServiceRecord, so we need to perform a null
+                            // check here.
+                            if (mAppForAllowingBgActivityStartsByStart != null) {
+                                mAppForAllowingBgActivityStartsByStart
+                                        .addOrUpdateAllowBackgroundActivityStartsToken(
+                                                this, getExclusiveOriginatingToken());
+                            }
                         } else {
                             Slog.wtf(TAG,
                                     "Service callback to revoke bg activity starts by service "