Line-break chars should not be rendered on Text & Font preview area

In the "Text and Font" dialog, the preview area renders the first line of the selected text object. It even nicely crops it and adds "..." if the line is too long to fit.

But it does not handle well the linebreak '\n' char. It renders a unicode codepoint symbol for U+000A, which is ugly and useless.

It would be much better to simply crop the string at that line break and be done with it.