Fix for stack imbalance bgmCompare parallel

[vandenman]

No description provided.

[vandenman]

@MaartenMarsman the code compiles but this R code crashes:

library(bgms)
x = Wenchuan[1:50, 1:5]
y = Wenchuan[1:50, c(1:4, 6)]
p = ncol(x)

samples1 = bgmCompare2(x, y, iter = 1000, nuts_max_depth = 10, cores = 4, chains = 4, seed = 1234)

any ideas?