"Save a Copy as Web Page..." don't save background color

If you have choosen the dark theme ("Edit" -> "Options..." -> "Theme" -> "Dark")  , then you can see, what I mean.
If you export then your code as HTML ("File" -> "Save a Copy as Web Page...") , the default background of the most browsers is white. And so you see nearly nothing.
So, in <body> the background color have to be set, too.
