ampute with run = FALSE produces error

[clayford]

Running ampute() with run = FALSE produces the following error:

Error in `[<-.data.frame`(`*tmp*`, is.na(data.frame(missing.data)), value = NA) : 
  unsupported matrix index in replacement

To Reproduce

set.seed(2016)
testdata <- as.data.frame(MASS::mvrnorm(n = 10000, 
                                        mu = c(10, 5, 0), 
                                        Sigma = matrix(data = c(1.0, 0.2, 0.2, 
                                                                0.2, 1.0, 0.2, 
                                                                0.2, 0.2, 1.0), 
                                                       nrow = 3, 
                                                       byrow = T)))
emptyresult <- ampute(testdata, run = FALSE)

Expected behavior
I expected to run ampute() without actually executing the amputation procedure as documented in the ampute vingette

Running mice version 3.18.0.