First of all we would like to pay your attention to the fact that this is just a warning, not an error. It occurs when the font doesn’t contain the description about the letters design. If this font is used in dynamic texts this warning will not result in serious problems. If the font is used in static texts then it will be lost with "Convert static text into shapes" option enabled.
So, we would recommend to disable "Convert static text into shapes" option if you notice this warning causes the text loss.