Bug: DAISIE_sim_cr_iw wrongly computes number of species at present

[Yangshen0325]

In DAISIE_sim_cr_iw(), the number of species at present is incorrectly calculated when cond > 0 and replicates > 1.
The number of species at present is obtained by counting the number of lineages on the island with a stac other than 0.
This calculation is wrong when there are multiple replicates. With each new replicate the number of species at present corresponds to the sum of the species at present for replicate 1 with those simulated during replicate 2.
The bug lies in lines 33 to 35 of DAISIE_sim_cr_iw.R

stac_vec <- unlist(island_replicates)[which(names(unlist(island_replicates)) == "taxon_list.stac")]
present <- which(stac_vec != 0)
number_present <- length(present)

This should read:

temp_island_replicates <- island_replicates[[rep]]
stac_vec <- unlist(temp_island_replicates)[which(names(unlist(temp_island_replicates)) == "taxon_list.stac")]
present <- which(stac_vec != 0)
number_present <- length(present)