### 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 ((ke.lParam & (1 << 24)) && (ke.wParam == VK_RETURN)) {
					
					keycode = Key::KP_ENTER;
				}
				Key key_label = keycode;
				Key physical_keycode = KeyMappingWindows::get_scansym((ke.lParam >> 16) & 0xFF, ke.lParam & (1 << 24));
				static BYTE keyboard_state[256];
				memset(keyboard_state, 0, 256);
				wchar_t chars[256] = {};
				UINT extended_code = MapVirtualKey((ke.lParam >> 16) & 0xFF, MAPVK_VSC_TO_VK_EX);
				if (!(ke.lParam & (1 << 24)) && ToUnicodeEx(extended_code, (ke.lParam >> 16) & 0xFF, keyboard_state, chars, 255, 4, GetKeyboardLayout(0)) > 0) {
					String keysym = String::utf16((char16_t *)chars, 255);
					if (!keysym.is_empty()) {
						key_label = fix_key_label(keysym[0], keycode);
					}
				}
				k->set_keycode(keycode);
				k->set_physical_keycode(physical_keycode);
				k->set_key_label(key_label);
				if (i + 1 < key_event_pos && key_event_buffer[i + 1].uMsg == WM_CHAR) {
					char32_t unicode = key_event_buffer[i + 1].wParam;
					static char32_t prev_wck = 0;
					if ((unicode & 0xfffffc00) == 0xd800) {
						if (prev_wck != 0) {
							ERR_PRINT("invalid utf16 surrogate input");
						}
						prev_wck = unicode;
						break; 
					} else if ((unicode & 0xfffffc00) == 0xdc00) {
						if (prev_wck == 0) {