Modified getCallerInfo() to handle silent ringtone

Bug: 12800232
Change-Id: I002c3df378cbaf367f212bf266d3682f6119daec

Modified code here so that it is consistent with framework/base/... and this module will be used in the future.
diff --git a/InCallUI/src/com/android/incallui/CallerInfo.java b/InCallUI/src/com/android/incallui/CallerInfo.java
index f15cb5d..1a52c50 100644
--- a/InCallUI/src/com/android/incallui/CallerInfo.java
+++ b/InCallUI/src/com/android/incallui/CallerInfo.java
@@ -241,7 +241,7 @@
                 // in the database.
                 columnIndex = cursor.getColumnIndex(PhoneLookup.CUSTOM_RINGTONE);
                 if ((columnIndex != -1) && (cursor.getString(columnIndex) != null)) {
-                    if (cursor.getString(columnIndex).equals("")) {
+                    if (TextUtils.isEmpty(cursor.getString(columnIndex))) {
                         // make it consistent with frameworks/base/.../CallerInfo.java
                         info.contactRingtoneUri = Uri.EMPTY;
                     } else {