Fix testSaw_ungrantedUid_Bluetooth

Keystore.saw returns [] on no result, not null, so the test was
incorrectly failing.

Change-Id: I22dcf85c5d6c5c0368848bc784c3215c092d9ea8
diff --git a/keystore/tests/src/android/security/KeyStoreTest.java b/keystore/tests/src/android/security/KeyStoreTest.java
index c9a140c..1487b39 100644
--- a/keystore/tests/src/android/security/KeyStoreTest.java
+++ b/keystore/tests/src/android/security/KeyStoreTest.java
@@ -294,14 +294,14 @@
 
     public void testSaw_ungrantedUid_Bluetooth() throws Exception {
         String[] results1 = mKeyStore.saw(TEST_KEYNAME, Process.BLUETOOTH_UID);
-        assertNull(results1);
+        assertEquals(0, results1.length);
 
         mKeyStore.password(TEST_PASSWD);
         mKeyStore.put(TEST_KEYNAME1, TEST_KEYVALUE, KeyStore.UID_SELF, KeyStore.FLAG_ENCRYPTED);
         mKeyStore.put(TEST_KEYNAME2, TEST_KEYVALUE, KeyStore.UID_SELF, KeyStore.FLAG_ENCRYPTED);
 
         String[] results2 = mKeyStore.saw(TEST_KEYNAME, Process.BLUETOOTH_UID);
-        assertNull(results2);
+        assertEquals(0, results2.length);
     }
 
     public void testSaw_grantedUid_Wifi() throws Exception {