title: Unable to eliminate Firebase Analytics Thread warnings using Xcode 9 in Swift
body: <p>After moving to <strong>Xcode 9</strong> with an existing project I’m keep receiving warnings from the <strong>Main Thread Checker</strong> about a queue called <code>FIRAnalyticsQueue</code>.
  I found this MTC as an awesome feature, since I’ve already resolved quite a lot threading issues with it, but unfortunately I’m not able to eliminate the one regarding to <strong>Firebase</strong> configuration.</p>
  
  <p>The code that I use in the <code>AppDelegate</code> <code>didFinishLaunchingWithOptions</code> function is the following:</p>
  
  <pre><code>if FIRApp.defaultApp() == nil {
     FIRApp.configure()
  }
  </code></pre>
  
  <p>And the log that I receives after evaluating the code above:</p>
  
  <pre><code>2017-10-05 16:14:34.965 PonySugarCandyApp[17721] &lt;Error&gt; [Firebase/Core][I-COR000003] The default Firebase app has not yet been configured. Add [FIRApp configure] to your application initialization.
  2017-10-05 16:14:45.283 PonySugarCandyApp[17721] &lt;Notice&gt; [Firebase/Analytics][I-ACS023007] Firebase Analytics v.3700000 started
  2017-10-05 16:14:52.139 PonySugarCandyApp[17721] &lt;Notice&gt; [Firebase/Analytics][I-ACS023008] To enable debug logging set the following application argument: -FIRAnalyticsDebugEnabled
  =================================================================
  Main Thread Checker: UI API called on a background thread: -[UIApplication delegate]
  PID: 17721, TID: 1309471, Thread name: (none), Queue name: FIRAnalyticsQueue, QoS: 9
  Backtrace:
  4   PonySugarCandyApp                   0x000000010c5fe721 __38+[FIRAnalytics createAppDelegateProxy]_block_invoke + 55
  5   libdispatch.dylib                   0x000000011337143c _dispatch_client_callout + 8
  6   libdispatch.dylib                   0x00000001133729c7 dispatch_once_f + 297
  7   PonySugarCandyApp                   0x000000010c5fd519 __47+[FIRAnalytics startWithConfiguration:options:]_block_invoke_2 + 101
  8   libdispatch.dylib                   0x00000001133703f7 _dispatch_call_block_and_release + 12
  9   libdispatch.dylib                   0x000000011337143c _dispatch_client_callout + 8
  10  libdispatch.dylib                   0x000000011337995b _dispatch_queue_serial_drain + 1162
  11  libdispatch.dylib                   0x000000011337a2df _dispatch_queue_invoke + 336
  12  libdispatch.dylib                   0x000000011337d1f9 _dispatch_root_queue_drain + 772
  13  libdispatch.dylib                   0x000000011337ce97 _dispatch_worker_thread3 + 132
  14  libsystem_pthread.dylib             0x00000001138345a2 _pthread_wqthread + 1299
  15  libsystem_pthread.dylib             0x000000011383407d start_wqthread + 13
  (Recorded stack frame) 
  </code></pre>