Don't crash in various ways when using backup services too early

BackupManager now no longer tries to use a null service binder if it's used
early during the boot process.  ActivityManagerService no longer tries to
dereference null pointers if bind/unbind semantics get out of step due to things
being run too early.

core/java/android/backup/BackupManager.java

@@ -68,9 +68,11 @@ public class BackupManager {
      * {@link android.app.BackupAgent} subclass will be scheduled when you call this method.
      */
     public void dataChanged() {
-        try {
-            mService.dataChanged(mContext.getPackageName());
-        } catch (RemoteException e) {
+        if (mService != null) {
+            try {
+                mService.dataChanged(mContext.getPackageName());
+            } catch (RemoteException e) {
+            }
         }
     }
 
@@ -83,9 +85,11 @@ public class BackupManager {
      */
     public IRestoreSession beginRestoreSession(int transportID) {
         IRestoreSession binder = null;
-        try {
-            binder = mService.beginRestoreSession(transportID);
-        } catch (RemoteException e) {
+        if (mService != null) {
+            try {
+                binder = mService.beginRestoreSession(transportID);
+            } catch (RemoteException e) {
+            }
         }
         return binder;
     }

services/java/com/android/server/am/ActivityManagerService.java

@@ -10472,8 +10472,17 @@ public final class ActivityManagerService extends ActivityManagerNative implemen
     // done with this agent
     public void unbindBackupAgent(ApplicationInfo appInfo) {
         if (DEBUG_BACKUP) Log.v(TAG, "unbindBackupAgent: " + appInfo);
+        if (appInfo == null) {
+            Log.w(TAG, "unbind backup agent for null app");
+            return;
+        }
 
         synchronized(this) {
+            if (mBackupAppName == null) {
+                Log.w(TAG, "Unbinding backup agent with no active backup");
+                return;
+            }
+
             if (!mBackupAppName.equals(appInfo.packageName)) {
                 Log.e(TAG, "Unbind of " + appInfo + " but is not the current backup target");
                 return;