I found something
The SVG image (which is a X) is there but we are just not seeing it because the CSS for the element: height size/position/padding is all to cock.

I seems to me this is not a very good way to do what you are trying to achieve, (which is a bit difficult for me to visualize without seeing the actual thing you are trying to do.
Unfortunately apart from I hardly ever use materialize framework (so I can't comment on how to fix it) I no longer have time to address this issue, hopefully someone more versed in the materialize framework will be able to chip in.