Fix: release lock in UserHistoryDictionary.

Change-Id: I050c252910c6b5b0a79cd2d52c525679f2d6091d

java/src/com/android/inputmethod/latin/UserHistoryDictionary.java

@@ -320,7 +320,11 @@ public final class UserHistoryDictionary extends ExpandableDictionary {
                     mUserHistoryDictionary.mBigramListLock.unlock();
                 }
             } else if (mUserHistoryDictionary.mBigramListLock.tryLock()) {
+                try {
                     doWriteTaskLocked();
+                } finally {
+                    mUserHistoryDictionary.mBigramListLock.unlock();
+                }
             }
             return null;
         }