Fixed NPE in RankingHelper.writeXml.

Make sure that mRecords is operated with the object lock.

Bug:127290258
Test: Repeat to upgrade the App targetversion from less than O to a later version
Change-Id: I70e61c0fcd3071f32a430d45441ffe1376147a5d
Signed-off-by: Ethan_Hu <huyuxin3818@gmail.com>
Merged-In: Ic7f676499425fe54453384d7c03de5d95c03a713

services/core/java/com/android/server/notification/RankingHelper.java

@@ -1401,11 +1401,14 @@ public class RankingHelper implements RankingConfig {
                 }
                 // Package upgrade
                 try {
-                    Record fullRecord = getRecord(pkg,
-                            mPm.getPackageUidAsUser(pkg, changeUserId));
-                    if (fullRecord != null) {
-                        createDefaultChannelIfNeeded(fullRecord);
-                        deleteDefaultChannelIfNeeded(fullRecord);
+                    synchronized (mRecords) {
+                        final String key = recordKey(pkg,
+                                mPm.getPackageUidAsUser(pkg, changeUserId));
+                        Record fullRecord = mRecords.get(key);
+                        if (fullRecord != null) {
+                            createDefaultChannelIfNeeded(fullRecord);
+                            deleteDefaultChannelIfNeeded(fullRecord);
+                        }
                     }
                 } catch (NameNotFoundException e) {}
             }