### Godot version

v4.0.beta17.mono.official [c40020513]

### System information

Windows 11 22H2

### Issue description

If a focused subwindow is destroyed, DisplayServerWindows may still attempt to send mouse motion events to that window, because `last_focused_window` isn't updated until another window is focused.

```
ERROR: Condition "!windows.has(p_window)" is true. Returning: Point2i()
   at: window_get_position (platform/windows/display_server_windows.cpp:999)
```

### Steps to reproduce

Run the MRP, click some non-Godot application window to focus it, then click the "CLOSE" button in the secondary window. This destroys the window without re-focusing the main window, so hovering the mouse over the main window will produce the error message above.

### Minimal reproduction project

[native_windows_hover.zip](https://github.com/godotengine/godot/files/10573386/native_windows_hover.zip)

reinterpret_cast<void *>(&wd));
		if (!wd.hWnd) {
			MessageBoxW(nullptr, L"Window Creation Error.", L"ERROR", MB_OK | MB_ICONEXCLAMATION);
			windows.erase(id);
			ERR_FAIL_V_MSG(INVALID_WINDOW_ID, "Failed to create Windows OS window.");
		}
		if (p_mode == WINDOW_MODE_FULLSCREEN || p_mode == WINDOW_MODE_EXCLUSIVE_FULLSCREEN) {
			wd.fullscreen = true;
			if (p_mode == WINDOW_MODE_FULLSCREEN) {
				wd.multiwindow_fs = true;
			}
		}
		if (p_mode != WINDOW_MODE_FULLSCREEN && p_mode != WINDOW_MODE_EXCLUSIVE_FULLSCREEN) {
			wd.pre_fs_valid = true;
		}
		if (is_dark_mode_supported() && dark_title_available) {
			BOOL value = is_dark_mode();
			::DwmSetWindowAttribute(wd.hWnd, DWMWA_USE_IMMERSIVE_DARK_MODE, &value, sizeof(value));
		}
#ifdef VULKAN_ENABLED
		if (context_vulkan) {
			if (context_vulkan->window_create(id, p_vsync_mode, wd.hWnd, hInstance, WindowRect.right - WindowRect.left, WindowRect.bottom - WindowRect.top) != OK) {
				memdelete(context_vulkan);
				context_vulkan = nullptr;
				windows.erase(id);
				ERR_FAIL_V_MSG(INVALID_WINDOW_ID, "Failed to create Vulkan Window.");
			}
			wd.context_created = true;
		}