title: iOS audio app freezes when disconnecting from Audiobus
body: <p>My app is locking up when disconnecting from Audiobus 3/AUM. I see this:</p>
  
  <p>2018-06-02 14:06:59.757468-0700 MyApp[269:9400] dnssd_clientstub read_all(14) DEFUNCT</p>
  
  <p>2018-06-02 14:06:59.761007-0700 MyApp[269:9351] TIC Read Status [1:0x1c41774c0]: 1:57</p>
  
  <p>2018-06-02 14:06:59.761087-0700 MyApp[269:9351] TIC Read Status [1:0x1c41774c0]: 1:57</p>
  
  <p>2018-06-02 14:06:59.764163-0700 MyApp[269:9400] dnssd_clientstub read_all(15) DEFUNCT</p>
  
  <p>I am subscribed to ABDisconnected, ABConnectionsChanged, and IAADisconnected notifications and am unable to intercept the problem. I am not shutting down my engine while AB is connected. I am vexed. I suspect that AudioKit is being shut down somehow without my permission. Is there perhaps a way I can observe changes to AudioKit's engine's isRunning property? AudioKit 4.2.4, Audiobus 3.0.4, iOS 11.4</p>