Small readability improvement (A100)

Change-Id: I6340748654a95d203ed43ceb9a7e6468b5b8ab1c
diff --git a/java/src/com/android/inputmethod/latin/BinaryDictionary.java b/java/src/com/android/inputmethod/latin/BinaryDictionary.java
index 7da2035..5ecebeb 100644
--- a/java/src/com/android/inputmethod/latin/BinaryDictionary.java
+++ b/java/src/com/android/inputmethod/latin/BinaryDictionary.java
@@ -125,8 +125,8 @@
 
         final int count;
         if (composer.size() <= 1) {
-            count = TextUtils.isEmpty(prevWord) ? -1 : getBigramsInternal(composer,
-                    prevWordCodePointArray);
+            if (TextUtils.isEmpty(prevWord)) return null;
+            count = getBigramsInternal(composer, prevWordCodePointArray);
         } else {
             count = getWordsInternal(composer, prevWordCodePointArray, proximityInfo);
         }