title: Crash on FIRApp.configure() method
body: <p>I added a firebase framework using cocoapods to existing Project but a crash occurs at the <code>FIRApp.configure()</code> method.</p>
  
  <p>To figure out the problem, I create a new project and add a firebase Framework which is working.</p>
  
  <p>I don't know what could be the Problem.</p>