### 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)

return 0;
			}
			if (GetRawInputData((HRAWINPUT)lParam, RID_INPUT, lpb, &dwSize, sizeof(RAWINPUTHEADER)) != dwSize) {
				OutputDebugString(TEXT("GetRawInputData does not return correct size !\n"));
			}
			RAWINPUT *raw = (RAWINPUT *)lpb;
			if (raw->header.dwType == RIM_TYPEMOUSE) {
				Ref<InputEventMouseMotion> mm;
				mm.instantiate();
				mm->set_window_id(window_id);
				mm->set_ctrl_pressed(control_mem);
				mm->set_shift_pressed(shift_mem);
				mm->set_alt_pressed(alt_mem);
				mm->set_pressure((raw->data.mouse.ulButtons & RI_MOUSE_LEFT_BUTTON_DOWN) ? 1.0f : 0.0f);
				mm->set_button_mask(last_button_state);
				Point2i c(windows[window_id].width / 2, windows[window_id].height / 2);
				
				POINT pos = { (int)c.x, (int)c.y };
				ClientToScreen(windows[window_id].hWnd, &pos);
				SetCursorPos(pos.x, pos.y);
				mm->set_position(c);
				mm->set_global_position(c);
				mm->set_velocity(Vector2(0, 0));
				if (raw->data.mouse.usFlags == MOUSE_MOVE_RELATIVE) {
					mm->set_relative(Vector2(raw->data.mouse.lLastX, raw->data.mouse.lLastY));
				} else if (raw->data.mouse.usFlags == MOUSE_MOVE_ABSOLUTE) {
					int nScreenWidth = GetSystemMetrics(SM_CXVIRTUALSCREEN);
					int nScreenHeight = GetSystemMetrics(SM_CYVIRTUALSCREEN);
					int nScreenLeft = GetSystemMetrics(SM_XVIRTUALSCREEN);
					int nScreenTop = GetSystemMetrics(SM_YVIRTUALSCREEN);