In some circumstances the code that renders thumbnails into cells can fail and that will abort the rendering of the entire grid.
See this forum post for instance: https://forum.openrefine.org/t/openrefine-3-7-9-released/1259/9?u=antonin_d
We should make sure that any exception thrown in our cell renderer is caught appropriately and a fallback is used, so that the rest of the grid is still rendered.
This safety mechanism should also be implemented on OpenRefine's side of the extension point.