Error on create page

when i try to create page than error occured and after that says, "The page [page_name] already exists" but actually there is no page on that name

Unhandled exception:
type 'String' is not a subtype of type 'Map' in type cast
#0 PubspecUtils._extraFolder. (package:get_cli/common/utils/pubspec/pubspec_utils.dart:46:32)
#1 _PubValue.value (package:get_cli/common/utils/pubspec/pubspec_utils.dart:172:26)
#2 PubspecUtils.extraFolder (package:get_cli/common/utils/pubspec/pubspec_utils.dart:57:48)
#3 CreatePageCommand._writeFiles (package:get_cli/commands/impl/create/page/page.dart:80:36)
#4 CreatePageCommand.checkForAlreadyExists (package:get_cli/commands/impl/create/page/page.dart:74:7)
#5 CreatePageCommand.execute (package:get_cli/commands/impl/create/page/page.dart:38:5)
#6 main (file:///C:/Users/appit/AppData/Local/Pub/Cache/git/get_cli-0cbdef3d191a49f371315fb6ab899e32dfc64358/bin/get.dart:18:23)
#7 _delayEntrypointInvocation. (dart:isolate-patch/isolate_patch.dart:295:33)
#8 _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)

1) Yes!
2) No
3) I want to rename
The page [page_name] already exists, do you want to overwrite it? [1]
Unhandled exception:
type 'String' is not a subtype of type 'Map' in type cast
#0 PubspecUtils._extraFolder. (package:get_cli/common/utils/pubspec/pubspec_utils.dart:46:32)
#1 _PubValue.value (package:get_cli/common/utils/pubspec/pubspec_utils.dart:172:26)
#2 PubspecUtils.extraFolder (package:get_cli/common/utils/pubspec/pubspec_utils.dart:57:48)
#3 CreatePageCommand._writeFiles (package:get_cli/commands/impl/create/page/page.dart:80:36)
#4 CreatePageCommand.checkForAlreadyExists (package:get_cli/commands/impl/create/page/page.dart:64:9)
#5 CreatePageCommand.execute (package:get_cli/commands/impl/create/page/page.dart:38:5)
#6 main (file:///C:/Users/appit/AppData/Local/Pub/Cache/git/get_cli-0cbdef3d191a49f371315fb6ab899e32dfc64358/bin/get.dart:18:23)
#7 _delayEntrypointInvocation. (dart:isolate-patch/isolate_patch.dart:295:33)
#8 _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)