### 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
bi.bV5Compression = BI_BITFIELDS;
		bi.bV5RedMask = 0x00ff0000;
		bi.bV5GreenMask = 0x0000ff00;
		bi.bV5BlueMask = 0x000000ff;
		bi.bV5AlphaMask = 0xff000000;
		HDC dc = GetDC(nullptr);
		HBITMAP bitmap = CreateDIBSection(dc, reinterpret_cast<BITMAPINFO *>(&bi), DIB_RGB_COLORS, reinterpret_cast<void **>(&buffer), nullptr, 0);
		HBITMAP mask = CreateBitmap(texture_size.width, texture_size.height, 1, 1, nullptr);
		bool fully_transparent = true;
		for (UINT index = 0; index < image_size; index++) {
			int row_index = floor(index / texture_size.width) + atlas_rect.position.y;
			int column_index = (index % int(texture_size.width)) + atlas_rect.position.x;
			if (atlas_texture.is_valid()) {
				column_index = MIN(column_index, atlas_rect.size.width - 1);
				row_index = MIN(row_index, atlas_rect.size.height - 1);
			}
			const Color &c = image->get_pixel(column_index, row_index);
			fully_transparent = fully_transparent && (c.a == 0.f);
			*(buffer + index) = c.to_argb32();
		}
		
		if (cursors[p_shape]) {
			DestroyIcon(cursors[p_shape]);
		}
		if (fully_transparent) {
			cursors[p_shape] = nullptr;
		} else {
			ICONINFO iconinfo;
			iconinfo.fIcon = FALSE;
			iconinfo.xHotspot = p_hotspot.x;