NPE fix in SyncStorageEngine

Null check while reading malformed authorities
from xml file.

Bug: 26513719
Change-Id: I3bfb718bbc84b27ddd98f7941c3ca2e356d27ec0
diff --git a/services/core/java/com/android/server/content/SyncStorageEngine.java b/services/core/java/com/android/server/content/SyncStorageEngine.java
index 8266c08..f8b6f57 100644
--- a/services/core/java/com/android/server/content/SyncStorageEngine.java
+++ b/services/core/java/com/android/server/content/SyncStorageEngine.java
@@ -1903,8 +1903,10 @@
                             if ("authority".equals(tagName)) {
                                 authority = parseAuthority(parser, version);
                                 periodicSync = null;
-                                if (authority.ident > highestAuthorityId) {
-                                    highestAuthorityId = authority.ident;
+                                if (authority != null) {
+                                    if (authority.ident > highestAuthorityId) {
+                                        highestAuthorityId = authority.ident;
+                                    }
                                 }
                             } else if (XML_TAG_LISTEN_FOR_TICKLES.equals(tagName)) {
                                 parseListenForTickles(parser);