Fix flakiness of testHasCarrierPrivilegesViaCarrierConfigs.

testHasCarrierPrivilegesViaCarrierConfigs may fail if current carrier
config is null in overrideConfig method. Adding a null check to avoid
it.

Bug: 146163445
Test: atest CtsTelephonyTestCases:TelephonyManagerTest
Change-Id: I1debb28a5f8ed0f97af1ff5c642d224189bd6a25
Merged-In: I1debb28a5f8ed0f97af1ff5c642d224189bd6a25
diff --git a/src/com/android/phone/CarrierConfigLoader.java b/src/com/android/phone/CarrierConfigLoader.java
index ef7f5b8..8098a61 100644
--- a/src/com/android/phone/CarrierConfigLoader.java
+++ b/src/com/android/phone/CarrierConfigLoader.java
@@ -596,6 +596,10 @@
             configToSend = mConfigFromDefaultApp[phoneId];
         }
 
+        if (configToSend == null) {
+            configToSend = new PersistableBundle();
+        }
+
         // mOverrideConfigs is for testing. And it will override current configs.
         PersistableBundle config = mOverrideConfigs[phoneId];
         if (config != null) {