MEID and MC should not be ""

Bug: 173029706
Test: atest TelephonyManagerTest
Change-Id: I66df0cb127bf2a2a98d5b517cd67fa0bca44c1b5
diff --git a/tests/tests/telephony/current/src/android/telephony/cts/TelephonyManagerTest.java b/tests/tests/telephony/current/src/android/telephony/cts/TelephonyManagerTest.java
index e53cafc..00053f0 100644
--- a/tests/tests/telephony/current/src/android/telephony/cts/TelephonyManagerTest.java
+++ b/tests/tests/telephony/current/src/android/telephony/cts/TelephonyManagerTest.java
@@ -1249,6 +1249,11 @@
             return;
         }
 
+        // mc and meid should either be null or supported. empty string is not expected even if
+        // the device does not support mc/meid.
+        assertNotEquals("", mc);
+        assertNotEquals("", meid);
+
         if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_TELEPHONY)) {
             if (mTelephonyManager.getPhoneType() == TelephonyManager.PHONE_TYPE_CDMA) {
                 assertEquals(meid.substring(0, 8), mc);