Cancel moved to avoid crash

Sources/Networking/SessionDataTask.swift

@@ -101,9 +101,6 @@ public class SessionDataTask {
         guard let callback = removeCallback(token) else {
             return
         }
-        if callbacksStore.count == 0 {
-            task.cancel()
-        }
         onCallbackCancelled.call((token, callback))
     }
 

Sources/Networking/SessionDelegate.swift

@@ -72,6 +72,7 @@ class SessionDelegate: NSObject {
             // No other callbacks waiting, we can clear the task now.
             if !task.containsCallbacks {
                 let dataTask = task.task
+                dataTask.cancel()
                 self.remove(dataTask)
             }
         }