title: terminating with uncaught exception of type std::__1::system_error: mutex lock failed: Invalid argument
body: <p>If my app in on foreground, then I open app switcher then for quit my app, it'll crash. In the console there are:</p>
  
  <pre><code>libc++abi.dylib: terminating with uncaught exception of type std::__1::system_error: mutex lock failed: Invalid argument
  </code></pre>
  
  <p>But if I bring it to background, then I open app switcher then for quit my app, it won't crash.</p>