Upload file is not working

I am using the same command to upload an Image to Backendless but I get this error and the app terminated.

Unsupported value: <Backendless.BackendlessFile: 0x282f1e3e0> of type Backendless.BackendlessFile
*** Assertion failure in -[backendless_sdk.BackendlessWtiter writeValue:], FlutterStandardCodec.mm:334
*** Terminating app due to uncaught exception ‘NSInternalInconsistencyException’, reason: ‘Unsupported value for standard codec’
*** First throw call stack:
(0x18489204c 0x19cf06f54 0x18614b6cc 0x10975c138 0x106e62850 0x106e62920 0x10975c7c0 0x109759890 0x106eab6d0 0x106e8addc 0x1069ccd94 0x10695c6e0 0x10695c7f0 0x185034b34 0x185045af8 0x184502914 0x184504660 0x184512b60 0x18484acd4 0x184804eac 0x1848183b8 0x1a01a838c 0x1871b86a8 0x186f377f4 0x104f6b984 0x106399a24)
libc++abi: terminating with uncaught exception of type NSException

• thread

  #1

  , queue = ‘com.apple.main-thread’, stop reason = signal SIGABRT
  frame

  #0:

  0x00000001babd4964 libsystem_kernel.dylib__pthread_kill + 8 libsystem_kernel.dylib__pthread_kill:
  → 0x1babd4964 <+8>: b.lo 0x1babd4984 ; <+40>
  0x1babd4968 <+12>: pacibsp
  0x1babd496c <+16>: stp x29, x30, [sp,

  #-0x10

  ]!
  0x1babd4970 <+20>: mov x29, sp
  Target 0: (Runner) stopped.
  Lost connection to device.

My codes in Flutter are these:

Uint8List file = await imageFile.readAsBytes();
await Backendless.files.saveFile(file, filePathName: ‘/StoreFiles/$ownerId/${imageFile.path.split(’/’).last}’).then((response) {
fileName = response.toString();

}).onError((error, stackTrace){
  print('savefile error: $error');
});

nd when I want to just simply upload it it says:

[VERBOSE-2:ui_dart_state.cc(209)] Unhandled Exception: PlatformException(6002, Unable to write bytes into file /opt/backendless/repo/f16241ba-7a18-f7d0-ff2f-3f9e30c90900/files/StoreFiles/C69992E1-8298-49B3-AFF8-12515841899D, Unable to write bytes into file /opt/backendless/repo/f16241ba-7a18-f7d0-ff2f-3f9e30c90900/files/StoreFiles/C69992E1-8298-49B3-AFF8-12515841899D, null)
#0 StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:607:7)
#1 MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:156:18)

#2 UploadImageToBackend.uploadImageToBackendless (package:retailers/data/upload_image/upload_image.dart:17:5)

#3 _ShowImageWidgetState.build. (package:retailers/ui/view_select_image/show_image_widget.dart:73:17)