Fix NPE's due to ContentProvider unavailability

Bug: 5039272
Bug: 5039228

Change-Id: I13abe01642d7165c324b6838a0f0c9d6ed8114cf
diff --git a/src/com/android/exchange/ExchangeService.java b/src/com/android/exchange/ExchangeService.java
index 82e952f..3b71656 100644
--- a/src/com/android/exchange/ExchangeService.java
+++ b/src/com/android/exchange/ExchangeService.java
@@ -496,7 +496,7 @@
         ContentResolver resolver = context.getContentResolver();
         Cursor c = resolver.query(Account.CONTENT_URI, Account.CONTENT_PROJECTION, null, null,
                 null);
-        if (c == null) return null;
+        if (c == null) return accounts;
         try {
             ContentValues cv = new ContentValues();
             while (c.moveToNext()) {
diff --git a/src/com/android/exchange/provider/MailboxUtilities.java b/src/com/android/exchange/provider/MailboxUtilities.java
index cf5eb97..fb3ec14 100644
--- a/src/com/android/exchange/provider/MailboxUtilities.java
+++ b/src/com/android/exchange/provider/MailboxUtilities.java
@@ -68,6 +68,7 @@
             Cursor childCursor = resolver.query(Mailbox.CONTENT_URI,
                     Mailbox.ID_PROJECTION, MailboxColumns.PARENT_SERVER_ID + "=? AND " +
                     accountSelector, selectionArgs, null);
+            if (childCursor == null) return;
             try {
                 while (childCursor.moveToNext()) {
                     parentFlags |= Mailbox.FLAG_HAS_CHILDREN | Mailbox.FLAG_CHILDREN_VISIBLE;
@@ -104,6 +105,7 @@
         Cursor cursor = context.getContentResolver().query(Mailbox.CONTENT_URI,
                 Mailbox.CONTENT_PROJECTION, MailboxColumns.SERVER_ID + "=? AND " + accountSelector,
                 new String[] {serverId}, null);
+        if (cursor == null) return;
         try {
             if (cursor.moveToFirst()) {
                 setFlagsAndChildrensParentKey(context, cursor, accountSelector);
@@ -130,6 +132,7 @@
         ContentResolver resolver = context.getContentResolver();
         Cursor parentCursor = resolver.query(Mailbox.CONTENT_URI, Mailbox.CONTENT_PROJECTION,
                 noParentKeySelection, null, null);
+        if (parentCursor == null) return;
         try {
             while (parentCursor.moveToNext()) {
                 setFlagsAndChildrensParentKey(context, parentCursor, accountSelector);