Merge pull request #635 from pushkarnk/sr2630

Author: swift-ci

Foundation/NSURLSession/NSURLSessionTask.swift

@@ -839,10 +839,13 @@ extension URLSessionTask {
             guard case .inMemory(let bodyData) = bodyDataDrain else {
                 fatalError("Task has data completion handler, but data drain is not in-memory.")
             }
+
             guard let s = session as? URLSession else { fatalError() }
-           
-            var data = Data(capacity: bodyData!.length)
-            data.append(Data(bytes: bodyData!.bytes, count: bodyData!.length)) 
+
+            var data = Data()
+            if let body = bodyData {
+                data = Data(bytes: body.bytes, count: body.length)
+            }
 
             s.delegateQueue.addOperation {
                 completion(data, response, nil)