[Cannot read property 'parentKey' of undefined] when uploading exported json mindmap

[deathemperor]

I clone the repo and run and got this error. Steps:

• create a mindmap
• export/download
• import the just downloaded mindmap

The https://awehook.github.io/blink-mind/ works file though.

simple-capture-error.ts:6 TypeError: Cannot read property 'parentKey' of undefined
    at Object.getKeyPath (index.ts:29)
    at expandTo (sheet-model-modifier.ts:138)
    at doc-model-modifier.ts:36
    at operation (operation.ts:173)
    at dispatch (controller.ts:72)
    at controller.ts:64
    at Controller.push../packages/core/src/controller.ts.Controller.run (controller.ts:106)
    at openNewDocModel (operation.ts:217)
    at dispatch (controller.ts:72)
    at controller.ts:64
captureError @ simple-capture-error.ts:6
dispatch @ controller.ts:72
(anonymous) @ controller.ts:64
push../packages/core/src/controller.ts.Controller.run @ controller.ts:106
push../packages/core/src/controller.ts.Controller.run @ controller.ts:108
openNewDocModel @ operation.ts:217
dispatch @ controller.ts:72
(anonymous) @ controller.ts:64
push../packages/core/src/controller.ts.Controller.run @ controller.ts:106
(anonymous) @ toolbar-item-openfile.tsx:16
Promise.then (async)
onClickOpenFile @ toolbar-item-openfile.tsx:10
handleClick @ toolbar-item.tsx:28
callCallback @ react-dom.development.js:336
invokeGuardedCallbackDev @ react-dom.development.js:385
invokeGuardedCallback @ react-dom.development.js:440
invokeGuardedCallbackAndCatchFirstError @ react-dom.development.js:454
executeDispatch @ react-dom.development.js:584
executeDispatchesInOrder @ react-dom.development.js:609
executeDispatchesAndRelease @ react-dom.development.js:713
executeDispatchesAndReleaseTopLevel @ react-dom.development.js:722
forEachAccumulated @ react-dom.development.js:694
runEventsInBatch @ react-dom.development.js:739
runExtractedPluginEventsInBatch @ react-dom.development.js:880
handleTopLevel @ react-dom.development.js:5803
batchedEventUpdates$1 @ react-dom.development.js:24401
batchedEventUpdates @ react-dom.development.js:1415
dispatchEventForPluginEventSystem @ react-dom.development.js:5894
attemptToDispatchEvent @ react-dom.development.js:6010
dispatchEvent @ react-dom.development.js:5914
unstable_runWithPriority @ scheduler.development.js:697
runWithPriority$2 @ react-dom.development.js:12149
discreteUpdates$1 @ react-dom.development.js:24417
discreteUpdates @ react-dom.development.js:1438
dispatchDiscreteEvent @ react-dom.development.js:5881