In etl_extract, "zero-length inputs cannot be mixed with those of non-zero length"

[wmay]

etl_extract produces an error if there are zero new files to download and it is called with an ellipsis argument,

Error in mapply(downloader::download, src[missing], lcl[missing], ... = ...) : 
  zero-length inputs cannot be mixed with those of non-zero length

This code will reproduce the error:

library(etl)
cities = etl('cities')
cities %>% etl_extract()
# No new files to extract
cities %>% etl_extract(quiet = TRUE)

[beanumber]

Confirmed. Thanks!