### 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
wd.wtlc.lcOutExtX = wd.wtlc.lcInExtX;
			wd.wtlc.lcOutOrgY = 0;
			wd.wtlc.lcOutExtY = -wd.wtlc.lcInExtY;
			wd.wtctx = wintab_WTOpen(wd.hWnd, &wd.wtlc, false);
			if (wd.wtctx) {
				wintab_WTEnable(wd.wtctx, true);
				AXIS pressure;
				if (wintab_WTInfo(WTI_DEVICES + wd.wtlc.lcDevice, DVC_NPRESSURE, &pressure)) {
					wd.min_pressure = int(pressure.axMin);
					wd.max_pressure = int(pressure.axMax);
				}
				AXIS orientation[3];
				if (wintab_WTInfo(WTI_DEVICES + wd.wtlc.lcDevice, DVC_ORIENTATION, &orientation)) {
					wd.tilt_supported = orientation[0].axResolution && orientation[1].axResolution;
				}
			} else {
				print_verbose("WinTab context creation failed.");
			}
		} else {
			wd.wtctx = 0;
		}
		if (p_mode == WINDOW_MODE_MAXIMIZED) {
			wd.maximized = true;
			wd.minimized = false;
		}
		if (p_mode == WINDOW_MODE_MINIMIZED) {
			wd.maximized = false;
			wd.minimized = true;
		}
		wd.last_pressure = 0;