Calculating mnl model with logitr package and receiving error

Question

I am trying to calculate a multinomial model in R with the logitr package. I have discrete choice experiment data set.

  CHOICE ID_resp alt price amadori aia fileni smarket bio aperto terra
1      1       1   1   8.9       1   0      0       0   1      0     0
2      0       1   2  13.9       0   1      0       0   0      1     0
3      0       1   3  18.9       0   0      1       0   0      0     1
4      0       1   4  23.9       0   0      0       1   0      0     0
5      0       1   5   0.0       0   0      0       0   0      0     0
6      0       1   1  23.9       1   0      0       0   0      0     0
  standard
1        0
2        0
3        0
4        1
5        0
6        1

The structure of the data is:

'data.frame':   26200 obs. of  12 variables:
 $ CHOICE  : Factor w/ 2 levels "0","1": 2 1 1 1 1 1 2 1 1 1 ...
 $ ID_resp : int  1 1 1 1 1 1 1 1 1 1 ...
 $ alt     : Factor w/ 5 levels "1","2","3","4",..: 1 2 3 4 5 1 2 3 4 5 ...
 $ price   : num  8.9 13.9 18.9 23.9 0 23.9 8.9 13.9 18.9 0 ...
 $ amadori : int  1 0 0 0 0 1 0 0 0 0 ...
 $ aia     : int  0 1 0 0 0 0 1 0 0 0 ...
 $ fileni  : int  0 0 1 0 0 0 0 1 0 0 ...
 $ smarket : int  0 0 0 1 0 0 0 0 1 0 ...
 $ bio     : int  1 0 0 0 0 0 1 0 0 0 ...
 $ aperto  : int  0 1 0 0 0 0 0 1 0 0 ...
 $ terra   : int  0 0 1 0 0 0 0 0 1 0 ...
 $ standard: int  0 0 0 1 0 1 0 0 0 0 ...

the formula for the model is:

mnl_model <- logitr(
  data = model_df, 
  outcome = "CHOICE", 
  obsID = "ID_resp",
  pars = c("price", "amadori","aia","fileni","smarket","bio","aperto"       
           ,"terra" ,"standard")
 )

However, I receive the following error Error in sum(x) : invalid 'type' (character) of argument