### 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)

}
		if (width >= big_icon_width) {
			if (colors >= big_icon_cc) {
				big_icon_index = i;
				big_icon_width = width;
				big_icon_cc = colors;
			}
		}
	}
	ERR_FAIL_COND_MSG(big_icon_index == -1, "No valid icons found!");
	if (small_icon_index == -1) {
		WARN_PRINT("No small icon found, reusing " + itos(big_icon_width) + "x" + itos(big_icon_width) + " @" + itos(big_icon_cc) + " icon!");
		small_icon_index = big_icon_index;
		small_icon_cc = big_icon_cc;
	}
	
	DWORD bytecount_big = icon_dir->idEntries[big_icon_index].dwBytesInRes;
	Vector<uint8_t> data_big;
	data_big.resize(bytecount_big);
	pos = icon_dir->idEntries[big_icon_index].dwImageOffset;
	f->seek(pos);
	f->get_buffer((uint8_t *)&data_big.write[0], bytecount_big);
	HICON icon_big = CreateIconFromResource((PBYTE)&data_big.write[0], bytecount_big, TRUE, 0x00030000);
	ERR_FAIL_COND_MSG(!icon_big, "Could not create " + itos(big_icon_width) + "x" + itos(big_icon_width) + " @" + itos(big_icon_cc) + " icon, error: " + format_error_message(GetLastError()) + ".");
	
	DWORD bytecount_small = icon_dir->idEntries[small_icon_index].dwBytesInRes;
	Vector<uint8_t> data_small;
	data_small.resize(bytecount_small);
	pos = icon_dir->idEntries[small_icon_index].dwImageOffset;
	f->seek(pos);