Fix NPE for RingtonePickerActivity in Wear

There is no id "add_new_sound_text in add_new_sound_item layout.
It can't find the TextView and cause NPE.

Bug: 178990696
Test: manual. Verified by the partner.
Change-Id: I222bf8fce2cbc79b4c185907d261c95f5654fa91

packages/SoundPicker/res/layout-watch/add_new_sound_item.xml

@@ -20,6 +20,7 @@
      Make the visibility to "gone" to prevent failures.
  -->
 <TextView xmlns:android="http://schemas.android.com/apk/res/android"
+        android:id="@+id/add_new_sound_text"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:minHeight="?android:attr/listPreferredItemHeightSmall"