c.DATRASraw: Avoid losing names(dimnames(Nage))

[kaskr]

Not critical - just inconvenient:

x <- readExchange( system.file("exchange","Exchange1.zip",package="DATRAS") )
x <- subset(x, Species=="Gadus morhua")
x <- addSpectrum(x)
spl <- split(x, x$Month)
names(dimnames(spl[[1]]$N)) ## OK
spl <- lapply(spl, addNage, ages=0:3)
names(dimnames(spl[[1]]$Nage)) ## OK
z <- do.call("c", spl)
names(dimnames(z$Nage)) ## oops - lost !
names(dimnames(z$N)) ## oops - lost !
df <- as.data.frame(z, response="Nage") ## Warning: Response matrix does not have a named column dimension (e.g. ageGroup or sizeGroup)