Sending a window to an empty space doesn't work

## Description

Moving a window to an empty Space no longer works. The same command works when the destination Space already contains at least one window.

Observed on macOS 26.4.1 (25E253).

## Reproduction steps
1. Create an empty space
2. Try moving an existing window to that space using `yabai -m window WINDOW_SEL --space EMPTY_SPACE_SEL`

## Expected behavior

The window should move to the chosen space regardless of whether it is empty or not.

## Actual behavior

The window stays in its current space if the destination space is empty.

## Environment

- yabai version: yabai-v7.1.25
- macOS version: 26.4.1 (25E253)
- Architecture: Apple Silicon
- Install method: Homebrew release
- SIP status: **disabled**:
```
Configuration:
Apple Internal: disabled
Kext Signing: enabled
Filesystem Protections: disabled
Debugging Restrictions: disabled
DTrace Restrictions: enabled
NVRAM Protections: disabled
BaseSystem Verification: enabled
Boot-arg Restrictions: disabled
Kernel Integrity Protections: enabled
Authenticated Root Requirement: enabled
```
- Scripting addition: **enabled**
- Displays: multiple (2)

## Configuration
I included only lines that might be relevant in my opinion. Let me know if you need all of them or specific ones:

```sh
sudo yabai --load-sa
yabai -m signal --add event=dock_did_restart action="sudo yabai --load-sa"
yabai -m config layout stack
yabai -m config mouse_follows_focus on
yabai -m config focus_follows_mouse autoraise
yabai -m config window_placement second_child
```

## Notes

* The issue only appears to happen when the destination Space is empty.
* The same command works when the destination Space already has a window.
* No visible error is printed by the command.

Start by reproducing `yabai -m window WINDOW_SEL --space EMPTY_SPACE_SEL` on macOS with both empty and populated destination Spaces, then trace the window-to-Space command handling. Compare the two paths and verify that the existing window moves to an empty Space without changing the behavior for populated Spaces.

Written by the indexing model from the issue text.