rbind a list of data.frames while keeping NULL elements in R

Question

I would like to rbind a list of data.frame and transform NULL elements into NA using R. Consider the following example,

Answer 1

Start with transforming the NULL elements:

l <- lapply(l, function(x) if(is.null(x)) data.frame(C1 = NA) else x)

dplyr::bind_rows(l)
#  C1 C2
#1  1  2
#2 NA NA
#3  3 NA