Bug in nNA()

[cvanderaa]

There is a bug in nNA() when one assay is empty.

Reproducible example

library(QFeatures)
data("feat2")
feat2[[1]] <- feat2[[1]][, FALSE, drop = FALSE]
nNA(feat2, 1:3)

Error in h(simpleError(msg, call)) : 
  error in evaluating the argument 'args' in selecting a method for function 'do.call': different row counts implied by arguments