PDF export - infinity symbol rendered as a question mark
In a PDF export of a Geogebra Diagram the infinity Symbol (looks approximately like an eight rotated by 90 degree) is rendered as a question mark.
The font used by Geogebra (Liberation Sans) has the infinity character (U221E). However it is not used.
How can I amend this? Can I?
PS) Possibly also other characters (like greek letters) are similarily affected. I have not tested this.