convert_Wavelength2Energy() fails on a RLum.Data.Spectrum object if order=TRUE

[mcol]

Running this snippet:

lambda <- seq(400,800,50)
data <- matrix(data = rep(1, 2 * length(lambda)), ncol = 2)
rownames(data) <- lambda
colnames(data) <- 1:ncol(data)
object <- set_RLum(class = "RLum.Data.Spectrum", data = data[,1,drop = FALSE])
convert_Wavelength2Energy(object, order = TRUE)

fails with:

Error in (function (cl, name, valueClass)  : 
  assignment of an object of class “numeric” is not valid for @‘data’ in an object of class “RLum.Data.Spectrum”; is(value, "matrix") is not TRUE

[mcol]

The error occurs at this line:

object@data <- object@data[order(as.numeric(rownames(object@data))), ]

because if object is of the RLum.Data.Spectrum class, it is a 1-column matrix, and the line above implicitly turns it into a vector, so the assignment fails. Adding drop=FALSE fixes the issue.

[RLumSK]

Fixes with PR #134