Can't do "by_stock = stocks, by_area = TRUE" in g3_parameterized

[lentinj]

stocks <- list(
  imm = g3_stock(c(species = 'bli', maturity = 'imm'), 1:10 * 10) |>
    g3s_age(minage = 2, maxage = 7) |>
    g3s_livesonareas(areas[c('a', 'b', 'c')])
)

g3_parameterized('Ka', by_stock = stocks, by_area = TRUE)

Error in g3_parameterized("Ka", by_stock = stocks, by_area = TRUE) :
  One of by_stock/by_predator should be set if by_area is set
Environment:
  1: g3_parameterized("Ka", by_stock = stocks, by_area = TRUE)
  2: stop("One of by_stock/by_predator should be set if by_area is set")

Not sure there's any reason this is missing, it should be easier than the currently-implemented cases, we need to dig out __areas from all supplied stocks, and use the intersection of them.