Dont crash on missing URLSessionTask.behaviour

Author: Anton Pogonets

Foundation/URLSession/TaskRegistry.swift

@@ -109,10 +109,7 @@ extension URLSession._TaskRegistry {
     ///
     /// - Note: It is a programming error to pass a task that isn't registered.
     /// - Note: This must **only** be accessed on the owning session's work queue.
-    func behaviour(for task: URLSessionTask) -> _Behaviour {
-        guard let b = behaviours[task.taskIdentifier] else {
-            fatalError("Trying to access a behaviour for a task that in not in the registry.")
-        }
-        return b
+    func behaviour(for task: URLSessionTask) -> _Behaviour? {
+        return behaviours[task.taskIdentifier]
     }
 }

Foundation/URLSession/URLSession.swift

@@ -557,13 +557,16 @@ internal extension URLSession {
 
     func behaviour(for task: URLSessionTask) -> _TaskBehaviour {
         switch taskRegistry.behaviour(for: task) {
-        case .dataCompletionHandler(let c): return .dataCompletionHandler(c)
-        case .downloadCompletionHandler(let c): return .downloadCompletionHandler(c)
-        case .callDelegate:
+        case .dataCompletionHandler(let c)?: return .dataCompletionHandler(c)
+        case .downloadCompletionHandler(let c)?: return .downloadCompletionHandler(c)
+        case .callDelegate?:
             guard let d = delegate as? URLSessionTaskDelegate else {
                 return .noDelegate
             }
             return .taskDelegate(d)
+        case .none:
+            NSLog("Trying to access a behaviour for a task that in not in the registry.")
+            return .noDelegate
         }
     }
 }