Use TextUtils.isEmpty() instead of null check.

If phoneNumber is empty string, we go to endless loop.

Test: ContactDisplayUtilsTest
PiperOrigin-RevId: 175573954
Change-Id: I449c851c65912de5d666efe27a41ffc37a52e5ff
diff --git a/java/com/android/contacts/common/util/ContactDisplayUtils.java b/java/com/android/contacts/common/util/ContactDisplayUtils.java
index ff22f28..a45394f 100644
--- a/java/com/android/contacts/common/util/ContactDisplayUtils.java
+++ b/java/com/android/contacts/common/util/ContactDisplayUtils.java
@@ -216,7 +216,7 @@
       return null;
     }
     final Spannable spannable = new SpannableString(message);
-    int start = phoneNumber == null ? -1 : message.indexOf(phoneNumber);
+    int start = TextUtils.isEmpty(phoneNumber) ? -1 : message.indexOf(phoneNumber);
     while (start >= 0) {
       final int end = start + phoneNumber.length();
       final TtsSpan ttsSpan = PhoneNumberUtilsCompat.createTtsSpan(phoneNumber);