Filter works incorrectly if fields are splitted by several log actions

Hello, I've debugged this issue https://github.com/logux/examples/issues/21 and found that there is a bug in the filters.
I can reproduce it with a simple test:

it('filter works correctly if sent not all fields', async () => {
  let client = new TestClient('10')
  await client.connect()
  client.log.keepActions()

  let posts = createFilter(client, Post, { authorId: '1'})
  let unbind = posts.listen(() => {})
  await allTasks()

  await client.server.sendAll({ channel: 'posts/1', type: 'logux/subscribed' })
  await client.server.sendAll({
    fields: { title: 'A' },
    id: '1',
    type: 'posts/created'
  })
  await client.server.sendAll({
    fields: { authorId: '1' },
    id: '1',
    type: 'posts/changed'
  })
  await allTasks()

  expect(ensureLoaded(posts.get()).list).toEqual([
    { id: '1', isLoading: false, title: 'A', authorId: '1' },
  ])
  unbind()
})

I want to fix it but I need some information on how that should work.
As I understand we need to accumulate log actions for an object until we receive the fields required for a filter.
What is the best way to achieve this?
Version: 0.21.1

Start from the createFilter entry point and the TestClient reproduction shown in the issue. Run the test with the posts/created and posts/changed actions split across log entries, then trace how filter state handles each action. Done means the accumulated fields produce one loaded post matching the expected list.