Currently, when the svg content contains errors, the XML reader throws an exception. Catch the exception and instead provide and event or another API that gives information about the error and allow the developers to handle the invalid SVG. The event should allow you to display nothing in case of error or replace the svg (by fixing it or creating your own geometry). A side effect of such event will be that you can use it to display your own error.
RadSvgImage control doesn't support the "em" font size unit (ex: font-size: 1.4em). Currently, it treats such font sizes as pixel units, which means that the final rendering font size for 1.4em will be 1.4px. Allow reading the "em" font sizes properly.