Fix NPE in getCallProviderLabel

Bug:18506544
Change-Id: I720e090bdda87904f61fa6fd0f1aa95844a4fe71
diff --git a/InCallUI/src/com/android/incallui/CallCardPresenter.java b/InCallUI/src/com/android/incallui/CallCardPresenter.java
index 5f1fe3b..b66f417 100644
--- a/InCallUI/src/com/android/incallui/CallCardPresenter.java
+++ b/InCallUI/src/com/android/incallui/CallCardPresenter.java
@@ -576,7 +576,8 @@
      */
     private String getCallProviderLabel(Call call) {
         PhoneAccount account = getAccountForCall(call);
-        if (account != null && getTelecomManager().hasMultipleCallCapableAccounts()) {
+        if (account != null && !TextUtils.isEmpty(account.getLabel())
+                && getTelecomManager().hasMultipleCallCapableAccounts()) {
             return account.getLabel().toString();
         }
         return null;