Fix issue with defaultModel singleton management

langid-java/src/main/java/com/carrotsearch/labs/langid/Model.java

@@ -175,10 +175,12 @@ public static synchronized Model defaultModel() {
 
       os.flush();
 
-      return Model.readExternal(
+      defaultModel = Model.readExternal(
           new ObjectInputStream(
               new ByteArrayInputStream(
                   os.toByteArray())));
+      return defaultModel;
+
     } catch (Exception e) {
       throw new RuntimeException("Default model not available.", e);
     } finally {