Error when deploying docker image to ECR by aws_cdk.DefaultStackSynthesizer

I try to deploy a docker image to ECR with the following code.

import os
import aws_cdk as cdk
from aws_cdk import (
    Stack,
    DefaultStackSynthesizer,
)
from constructs import Construct

dirname=os.getcwd();

class HelloStack(Stack):
    def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
        super().__init__(scope, construct_id, **kwargs)

        ecr=DefaultStackSynthesizer(
          image_assets_repository_name="rep-test"
        );
        ecr.add_docker_image_asset(
          source_hash="test",
          directory_name=dirname,
          docker_build_target="img_test"
        );

app = cdk.App()
HelloStack(app, "HelloStack")
app.synth()

But I got the following error. What is wrong? How can I solve this problem?

Traceback (most recent call last):
  File "app.py", line 26, in <module>
    HelloStack(app, "HelloStack")
  File "/home/bitnami/env/lib/python3.7/site-packages/jsii/_runtime.py", line 86, in __call__
    inst = super().__call__(*args, **kwargs)
  File "app.py", line 22, in __init__
    docker_build_target="img_test"
  File "/home/bitnami/env/lib/python3.7/site-packages/aws_cdk/__init__.py", line 23050, in add_docker_image_asset
    return typing.cast(DockerImageAssetLocation, jsii.invoke(self, "addDockerImageAsset", [asset]))
  File "/home/bitnami/env/lib/python3.7/site-packages/jsii/_kernel/__init__.py", line 143, in wrapped
    return _recursize_dereference(kernel, fn(kernel, *args, **kwargs))
  File "/home/bitnami/env/lib/python3.7/site-packages/jsii/_kernel/__init__.py", line 359, in invoke
    args=_make_reference_for_native(self, args),
  File "/home/bitnami/env/lib/python3.7/site-packages/jsii/_kernel/providers/process.py", line 359, in invoke
    return self._process.send(request, InvokeResponse)
  File "/home/bitnami/env/lib/python3.7/site-packages/jsii/_kernel/providers/process.py", line 326, in send
    raise JSIIError(resp.error) from JavaScriptError(resp.stack)
jsii.errors.JSIIError: Cannot read properties of undefined (reading 'account')