Dialer: Voicemail: Don't tear down the app

* When we populate the app with the simulator component and try to
  play a voicemail, it takes down the app die to the component name
  being null
* Check it before using it

Change-Id: I0de3a611f1ac82198a35de98954d6609eacbeca5
diff --git a/java/com/android/voicemail/impl/fetch/FetchVoicemailReceiver.java b/java/com/android/voicemail/impl/fetch/FetchVoicemailReceiver.java
index 147f323..f7a6084 100644
--- a/java/com/android/voicemail/impl/fetch/FetchVoicemailReceiver.java
+++ b/java/com/android/voicemail/impl/fetch/FetchVoicemailReceiver.java
@@ -117,14 +117,15 @@
             }
           }
 
-          phoneAccount =
-              new PhoneAccountHandle(
-                  ComponentName.unflattenFromString(cursor.getString(PHONE_ACCOUNT_COMPONENT_NAME)),
-                  cursor.getString(PHONE_ACCOUNT_ID));
-          TelephonyManager telephonyManager =
-              context
-                  .getSystemService(TelephonyManager.class)
-                  .createForPhoneAccountHandle(phoneAccount);
+          TelephonyManager telephonyManager = null;
+          ComponentName componentName = ComponentName.unflattenFromString(
+                  cursor.getString(PHONE_ACCOUNT_COMPONENT_NAME));
+          if (componentName != null) {
+            phoneAccount =
+                    new PhoneAccountHandle(componentName, cursor.getString(PHONE_ACCOUNT_ID));
+            telephonyManager = context.getSystemService(TelephonyManager.class)
+                    .createForPhoneAccountHandle(phoneAccount);
+          }
           if (telephonyManager == null) {
             // can happen when trying to fetch voicemails from a SIM that is no longer on the
             // device