flutter run fails after running the integration tests

[jibel]

Test Case

1. cd packages/ubuntu_desktop_installer/
2. Run the installer in dry mode and verify that it works:

flutter run

4. Run the integration tests:
   SUBIQUITY_REPLAY_TIMESCALE=100 flutter test integration_test/
5. Run the installer again

flutter run

On the second run, it fails with:

flutter: DEBUG subiquity_client: GET http://localhost/refresh?wait=true
flutter: DEBUG refresh: RefreshState.error(error: checkRefresh() returned error 500
Traceback (most recent call last):
  File "/home/u/udi/ubuntu-desktop-installer/vendor/ubuntu-desktop-provision/packages/subiquity_client/subiquity/subiquity/common/api/server.py", line 163, in handler
    result = await implementation(**args)
  File "/home/u/udi/ubuntu-desktop-installer/vendor/ubuntu-desktop-provision/packages/subiquity_client/subiquity/subiquity/server/controllers/refresh.py", line 233, in GET
    await self.check_task.wait()
AttributeError: 'NoneType' object has no attribute 'wait'
)

It'll ruin again after the deletion of .subiquity

rm -Rf ../../vendor/ubuntu-desktop-provision/packages/subiquity_client/subiquity/.subiquity/