### Godot version

4.0.beta12

### System information

Windows 11, RTX 3080

### Issue description

When a Window Node is created with it's Transparent flag set to true and Project Settings --> Display --> Window --> Subwindows --> Embed Subwindows is false, the Window has a black background. By cycling the transparent flag from false and back to true again, during runtime, the window's background then becomes transparent. 

### Steps to reproduce

Attempt to create a Non-embedded Subwindow with a transparent background using the appropriate flags. 

### Minimal reproduction project

Note: this project is from Reddit user [gongpha](https://www.reddit.com/user/gongpha/) and his Reddit post [Learning a Godot 4.0 Window node](https://www.reddit.com/r/godot/comments/xr8yxn/learning_a_godot_40_window_node/)

https://github.com/gongpha/godot4-window-test
if (LOWORD(wParam) == WA_ACTIVE || LOWORD(wParam) == WA_CLICKACTIVE) {
		_send_window_event(windows[p_window_id], WINDOW_EVENT_FOCUS_IN);
		windows[p_window_id].window_focused = true;
		alt_mem = false;
		control_mem = false;
		shift_mem = false;
		
		_set_mouse_mode_impl(mouse_mode);
	} else { 
		Input::get_singleton()->release_pressed_events();
		_send_window_event(windows[p_window_id], WINDOW_EVENT_FOCUS_OUT);
		windows[p_window_id].window_focused = false;
		alt_mem = false;
	}
	if ((tablet_get_current_driver() == "wintab") && wintab_available && windows[p_window_id].wtctx) {
		wintab_WTEnable(windows[p_window_id].wtctx, GET_WM_ACTIVATE_STATE(wParam, lParam));
	}
}
void DisplayServerWindows::_process_key_events() {
	for (int i = 0; i < key_event_pos; i++) {
		KeyEvent &ke = key_event_buffer[i];
		switch (ke.uMsg) {
			case WM_CHAR: {
				
				if (!KeyMappingWindows::is_extended_key(ke.wParam) && ((i == 0 && ke.uMsg == WM_CHAR) || (i > 0 && key_event_buffer[i - 1].uMsg == WM_CHAR))) {
					static char32_t prev_wc = 0;
					char32_t unicode = ke.wParam;
					if ((unicode & 0xfffffc00) == 0xd800) {
						if (prev_wc != 0) {