1d Gauss example -- returns log(Z)=-0.32, instead of 0?

Dear Brendon,

I would like to use your Diffusive Nested Sampling technique. To start, I created an extremely simple example -- a 1d Gaussian. However, I get incorrect results: It returns log(Z)=-0.32, instead of 0. Could you please help me figure out what I did wrong?
Also, do you have advice on how to build the perturb() function for a given problem? So far, I reused the multi-scale loguniform/Gaussian from SpikeSlab. I am also unsure in which cases not to return 0.

Kind regards,
                       Johannes