Fix NPE

bug: 3446590
Change-Id: Iea5bd8f63f3322496b5d68539f0215d5d01e68d1
diff --git a/java/src/com/android/inputmethod/latin/UserDictionary.java b/java/src/com/android/inputmethod/latin/UserDictionary.java
index 56ee5b9..db5d924 100644
--- a/java/src/com/android/inputmethod/latin/UserDictionary.java
+++ b/java/src/com/android/inputmethod/latin/UserDictionary.java
@@ -138,7 +138,7 @@
 
     private void addWords(Cursor cursor) {
         clearDictionary();
-
+        if (cursor == null) return;
         final int maxWordLength = getMaxWordLength();
         if (cursor.moveToFirst()) {
             final int indexWord = cursor.getColumnIndex(Words.WORD);