Key value lost when subsetting with non-existing key value and deselecting columns #3245

library(data.table)

dt <- data.table(
  symbol = rep(c("A", "B", "C"), each = 2), 
  group = rep(1:3, each = 2), 
  x = rnorm(6), 
  key = "symbol")
dt["A"]
#>    symbol group           x
#> 1:      A     1  0.01317652
#> 2:      A     1 -0.42823586
dt["A", -"group"]
#>    symbol           x
#> 1:      A  0.01317652
#> 2:      A -0.42823586
dt["D"]
#>    symbol group  x
#> 1:      D    NA NA
dt["D", -"group"]
#>    symbol  x
#> 1:   <NA> NA