### 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
k->set_unicode(0);
					}
					Input::get_singleton()->parse_input_event(k);
				} else {
					
				}
			} break;
			case WM_KEYUP:
			case WM_KEYDOWN: {
				Ref<InputEventKey> k;
				k.instantiate();
				k->set_window_id(ke.window_id);
				k->set_shift_pressed(ke.shift);
				k->set_alt_pressed(ke.alt);
				k->set_ctrl_pressed(ke.control);
				k->set_meta_pressed(ke.meta);
				k->set_pressed(ke.uMsg == WM_KEYDOWN);
				if ((ke.lParam & (1 << 24)) && (ke.wParam == VK_RETURN)) {
					
					k->set_keycode(Key::KP_ENTER);
				} else {
					k->set_keycode((Key)KeyMappingWindows::get_keysym(ke.wParam));
				}
				k->set_physical_keycode((Key)(KeyMappingWindows::get_scansym((ke.lParam >> 16) & 0xFF, ke.lParam & (1 << 24))));
				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");