Fix for NPE at isPremiumCapabilityAvailableForPurchase

Bug: 259405165
Test: atest android.telephony5.cts.TelephonyManagerReadNonDangerousPermissionTest#testPremiumCapabilities

Change-Id: I9f23d06e4fce0ae80e072f09a0d15aa31e05bead
diff --git a/src/com/android/phone/PhoneInterfaceManager.java b/src/com/android/phone/PhoneInterfaceManager.java
index 8cc004e..170d86d 100644
--- a/src/com/android/phone/PhoneInterfaceManager.java
+++ b/src/com/android/phone/PhoneInterfaceManager.java
@@ -11294,6 +11294,10 @@
         }
 
         Phone phone = getPhone(subId);
+        if (phone == null) {
+            loge("isPremiumCapabilityAvailableForPurchase: phone is null, subId=" + subId);
+            return false;
+        }
         final long identity = Binder.clearCallingIdentity();
         try {
             return SlicePurchaseController.getInstance(phone)