AppOpsCallback: do not log error on null package name

Java side can pass 'null' as packageName parameter for
IAppOpsCallback::opChanged, e.g. when calling it via
AppOpsService.notifyWatchersOfChange.

BnAppOpsCallback on the native side should not emit
"Reading a NULL string not supported here" error logs in
this case. For that, a different overload of
'Parcel::readString16' method must be used.

Bug: 130038586
Test: turn DND on / off, watch logcat
Change-Id: I69d28d6a998d75acf987bf49fb0cbfb75cb95828
diff --git a/libs/binder/IAppOpsCallback.cpp b/libs/binder/IAppOpsCallback.cpp
index 2f4dbee..aba4967 100644
--- a/libs/binder/IAppOpsCallback.cpp
+++ b/libs/binder/IAppOpsCallback.cpp
@@ -57,7 +57,8 @@
         case OP_CHANGED_TRANSACTION: {
             CHECK_INTERFACE(IAppOpsCallback, data, reply);
             int32_t op = data.readInt32();
-            String16 packageName = data.readString16();
+            String16 packageName;
+            (void)data.readString16(&packageName);
             opChanged(op, packageName);
             reply->writeNoException();
             return NO_ERROR;