we use a default style that sets a background and foreground color for most scenarios. If another style only modifies the foreground color, the background color remains null. According to your documentation the background color from the default style should be applied then.
However this only works if the token is surrounded by whitespaces. This specifically doesn't work for the first token in any given line, unless it is a whitespace.
As a workaround we use the background from our default style as fallback instead of null. But it would be easier if we just could use null instead.
Best regards, Tobias Lingemann.