ofxEditableSVG - problem with colon in attribute name

I updated the ofxEditableSVG addon slightly to allow for id attribute being added to <g> elements.

But during this process I learned that creating attributes that have a colon in their name, like
groupElement->setAttribute("inkscape:groupmode","layer");
crashes here:

With this error message:

libc++abi.dylib: terminating with uncaught exception of type Poco::XML::SAXParseException: SAXParseException

Is there away to make this work or does SVG and XML not allow for that?
I read something about this here: google chrome - Why do colons in linearGradient IDs break them when the SVG is used in an <img> tag? - Stack Overflow

A workaround is to open the file as text document and just replace things.

            ofBuffer buffer = ofBufferFromFile("svgs/"+newFileName);
            if(buffer.size()) {
                string content = buffer.getText();
                ofStringReplace(content, "inkscape-label", "inkscape:label");
                ofStringReplace(content, "inkscape-groupmode", "inkscape:groupmode");
                buffer.clear();
                buffer.set(content);
                ofBufferToFile("svgs/"+newFileName, buffer);
            }else{
                ofLog()<<("svgs/"+newFileName)<<" is empty !!!";
            }