Returns first element of list that it not NULL, recursively.
coalesce_r(x)Either an atomic vector of length 1 or a (potentially nested) list.
(list), either of atomic vectors or of named lists
Given a list of atomic vectors, the first non-null element is returned.
Given a list of lists, for all names found in all elements of the list
the first non-null element of a given name is returned.
This function is used internally in c.teal_slices to manage teal_slices attributes.