Throws exception if player returns false when playing at time

LeCountdown/Sound/DelaySoundPlayer.swift

@@ -48,6 +48,10 @@ import AVFoundation
         let time: TimeInterval = self._player.deviceCurrentTime + duration
         let result = self._player.play(atTime: time)
         FileLogger.log("play \(String(describing: self._player.url)) >atTime: \(time), result = \(result), isMainThread = \(Thread.isMainThread)")
+        
+        if !result {
+            throw SoundPlayerError.playReturnedFalse
+        }
     }
     
     func stop() {

LeCountdown/Sound/SoundPlayer.swift

@@ -31,6 +31,7 @@ struct SoundFile {
 enum SoundPlayerError : Error {
     case missingResourceError(file: SoundFile)
     case badFileName(name: String)
+    case playReturnedFalse
 }
 
 @objc class SoundPlayer: NSObject, AVAudioPlayerDelegate {