Conditional og rendering

[Rodrigo Hernangómez]

Currently there are no virus variant zones, so the list of "red countries" is empty. This causes an error in the og image rendering:

Error: Error: The shape level1 only contains empty units.

I have uncommented the og_image rendering in trigger.R at
7cc25dc
to stop the error. Ideally we should first check if the shapes are empty before proceeding further with them