This is an old coalesce functions for its arguments. It was actually
called coalesce, but now dplyr has also one of those. So let's just
The first_non_null function takes any number of arguments and returns the
first argument that is not null (i.e., NA). If all arguments are null, the
function returns NULL.
first_non_null(...)One or more arguments of any type.
The first non-null argument or NULL if all arguments are null.