Maximizing dispersion can crash when using default algorithm

[m-Py]

This makes the R session crash quite reliably (about at least once every ten attempts):

library(anticlust)

N <- 100
K <- N/2

cannot_link <- c(1, rep(2:(N-1), each = 2), N)
cannot_link <- matrix(cannot_link, ncol = 2, byrow = TRUE)
cannot_link <- rbind(cannot_link, t(apply(cannot_link, 1, rev)))
mat <- matrix(1, nrow = N, ncol = N)
mat[cannot_link] <- -1
anticlustering(mat, K = K, objective = "dispersion")

I get

 *** caught segfault ***
address (nil), cause 'unknown'

[m-Py]

Just using K = 2 also seems to work.