Getting an error while running mpc2$solve_mpc()

Hi, I am running the sample code after installing EMPC from GitHub. Somehow, getting the below error:

Error in prob_data$h[(nh + 1 - ny * N):nh] <- as.vector(yrefN) * yrefactor : 
  replacement has length zero

Any idea how to resolve this? I am using the first example of EMPC from the site.