Querying `undefined` as default language if focus out during QuickPick

## 🐛 Bug Report

## To Reproduce

When quickpicking language, if click other areas to cancel the selection, an undefined default language query will pop out:

![](https://user-images.githubusercontent.com/20227484/54933845-644d1380-4f58-11e9-82eb-4d58991b9adb.png)

## Expected behavior

Won't query for default language if no valid language is selected.
