[Bug] Moving a page that has an existing document block will send it to the trash can instead

### Bug Description

In some cases, a document block may disappear and send its page to the trash, instead of just moving to the destination.

### How to Reproduce

Case 1:
- add a page block using `/document`
- move the new page to another one by dragging and dropping using the sidebar
- The block will disappear, and its page will be moved to the trash instead of the destination page

Case 2:
- Add two page blocks using `/document`
- Put them side by side in a 2 column style by dragging and dropping
- use CTRL+Z to revert
- The block on the left side will disappear, and its page will be sent to the trash

### Expected Behavior

A page should not be deleted simply by being moved around or undoing.

Since it has a document block, that block should also move to the new page parent.

### Operating System

Window 10

### AppFlowy Version(s)

0.8.7

### Screenshots

_No response_

### Additional Context

_No response_

Reproduce both cases with a /document page block: move it through the sidebar, then try the two-column move and CTRL+Z sequence. Trace the page and document-block handling reached by drag-and-drop and undo; done means the block and page remain intact and the page moves to the intended parent rather than the trash.

Written by the indexing model from the issue text.