Guard against potential NPE.

Change-Id: I379da1f478b1b1fd1e488dbeff249cc10e3d48d5

src/com/android/email/service/EmailServiceStub.java

@@ -525,7 +525,9 @@ public abstract class EmailServiceStub extends IEmailService.Stub implements IEm
             // 3.  loop through the available messages and send them
             while (c.moveToNext()) {
                 long messageId = -1;
+                if (moveToSentValues != null) {
                     moveToSentValues.remove(EmailContent.MessageColumns.FLAGS);
+                }
                 try {
                     messageId = c.getLong(0);
                     // Don't send messages with unloaded attachments