title: got Must call FIRApp.configure() before using FIRDatabase. error even though i already called it
body: <p>I got 'Must call FIRApp.configure() before using FIRDatabase' error even though I already called it in the 'Appdelegate.swift'.<a href="http://i.stack.imgur.com/vzskq.jpg" rel="noreferrer">This is my app delegate</a></p>