Add some logging to show why audio tone is not present.

Test: build
Bug: 194889768
Change-Id: I224c5a210a86ca61c3732409e34af96715ecee48
diff --git a/src/com/android/server/telecom/RingtoneFactory.java b/src/com/android/server/telecom/RingtoneFactory.java
index d3d2d0e..d416376 100644
--- a/src/com/android/server/telecom/RingtoneFactory.java
+++ b/src/com/android/server/telecom/RingtoneFactory.java
@@ -85,8 +85,14 @@
             if (UserManager.get(contextToUse).isUserUnlocked(contextToUse.getUserId())) {
                 defaultRingtoneUri = RingtoneManager.getActualDefaultRingtoneUri(contextToUse,
                         RingtoneManager.TYPE_RINGTONE);
+                if (defaultRingtoneUri == null) {
+                    Log.i(this, "getRingtone: defaultRingtoneUri for user is null.");
+                }
             } else {
                 defaultRingtoneUri = Settings.System.DEFAULT_RINGTONE_URI;
+                if (defaultRingtoneUri == null) {
+                    Log.i(this, "getRingtone: Settings.System.DEFAULT_RINGTONE_URI is null.");
+                }
             }
             if (defaultRingtoneUri == null) {
                 return null;