Error in { : task 1 failed - "argument is of length zero" in rfe-svm using ROC

Question

library(LiblineaR)
library(kernlab)
library(caret)
packageVersion('caret')
library(doMC)
registerDoMC(cores=4)

# load dataset
iris <- iris[1:100,]
iris$Species <- as.factor(as.character(iris$Species))

# set parameters
crsvalidation<-2
subsetsize<-2
cost<-c(2^-20)
rfe.grid<-expand.grid(cost=cost, weight=c(1.571, 0.6367), Loss="hinge loss")

# use ROC measure
caretFuncs$summary<-twoClassSummary

# define parameters for recursive feature elimiation
rfeCtrl = rfeControl(functions=caretFuncs,
                     number=crsvalidation, method="cv", verbose=T, rerank=T,
                     saveDetails=T, allowParallel=T)

# define parameters for training
tCtrl = trainControl(classProbs = TRUE,summaryFunction = twoClassSummary, allowParallel = T)

# run model 
rfe(iris[,-5], iris[,5], sizes = subsetsize,
  rfeControl=rfeCtrl,
  #pass option to train()
  trainControl=tCtrl, metric="ROC",
  maximize=T,method="svmLinearWeights2",
  tuneGrid=rfe.grid, scale=T, preProc=NULL)

All the prints I've inserted were printed successfully except that I got the error: Error in { : task 1 failed - "argument is of length zero"

Note that if I don't add the inserts I will get a different error (run ignoring the contents between the dash lines): Error in { : task 1 failed - "undefined columns selected"

Update I printed the stack trace and got this error, the error is associated with the last line rfe(iris[,-5], iris[,5], sizes = subsetsize...):

 at stop(simpleError(msg, call = expr))
  at e$fun(obj, substitute(ex), parent.frame(), e$data)
  at foreach(iter = seq(along = resampleIndex), .combine = "c", .verbose = FALSE
  at nominalRfeWorkflow(x, y, sizes, ppOpts = NULL, ctrl = rfeControl, lev = cla
  at rfe.default(iris[, -5], iris[, 5], sizes = subsetsize, rfeControl = rfeCtrl
  at rfe(iris[, -5], iris[, 5], sizes = subsetsize, rfeControl = rfeCtrl, trainC
  at #3: assign(paste0("aa.m.train.rfe.", i, sep = ""), rfe(iris[, -5], iris[, 5
  at withVisible(expr)
  at #41: withCallingHandlers(withVisible(expr), debug = logger, message = logge
  at withJavaLogging({
    for (i in cost) {
        rfe.grid <- expand.grid(cos
Error in { : task 1 failed - "undefined columns selected"

Can anyone try to explain what happened?