Fix testCreateFromPdu() to test for the correct behavior for null input.

For null pdu, SmsMessage returned by createFromPdu() should be null.

Bug: 30120211
Change-Id: Ifc23c489e5f6a9a0699ed5c9250eb26e20657c93
diff --git a/tests/tests/telephony/src/android/telephony/cts/SmsMessageTest.java b/tests/tests/telephony/src/android/telephony/cts/SmsMessageTest.java
index 2406ad8..e247775 100644
--- a/tests/tests/telephony/src/android/telephony/cts/SmsMessageTest.java
+++ b/tests/tests/telephony/src/android/telephony/cts/SmsMessageTest.java
@@ -114,7 +114,7 @@
 
         // Test create from null Pdu
         sms = SmsMessage.createFromPdu(null, SmsMessage.FORMAT_3GPP);
-        assertNotNull(sms);
+        assertNull(sms);
 
         // Test create from long Pdu
         pdu = "07912160130310F2040B915121927786F300036060924180008A0DA"