Crash at maxevals=100

This gives a segmentation fault error: 

    using Cuba 
    vegas((x, f) -> f[1] = cos(x[1]), maxevals=100)

It works fine at 1000, and also this works fine: 

    vegas((x, f) -> f[1] = cos(x[1]), nstart=99, nincrease=99, maxevals=100)

I get a similar error from other functions (suave, divonne, cuhre) at `maxevals=100`. 

Cuba 0.4.0, Julia 0.6.0, on a mac. 