I’ve been working with rstanarm and loo for several months, just updated to the newest versions a couple weeks ago, and since then have started seeing this error message when running the `loo`

function:

```
> l_full5 <- loo(full5, k_threshold = 0.7)
1 problematic observation(s) found.
Model will be refit 1 times.
Fitting model 1 out of 1 (leaving out observation 2252)
Error in new_CppObject_xp(fields$.module, fields$.pointer, ...) :
Exception: model_bernoulli_namespace::model_bernoulli: N[k0__] is 0, but must be greater than or equal to 1 (in 'model_bernoulli' at line 12)
failed to create the sampler; sampling not done
Error in check_stanfit(stanfit) :
Invalid stanfit object produced please report bug
```

This only happens when a problematic observation(s) is/are found, and furthermore, seems to happen every time a problematic observation is found. This is happening for the more complex models I’m using.

Here are the data I’m using: dat_with_soil2.csv (865.8 KB),

and code that should reproduce the problem:

```
dat$BAc5 <- scale(dat$BAc5)
dat$BAh5 <- scale(dat$BAh5)
dat$n_con <- scale(dat$n_con)
dat$n_het <- scale(dat$n_het)
dat$gap <- scale(dat$gap)
dat$ph <- scale(dat$ph)
dat$tec <- scale(dat$tec)
dat$org <- scale(dat$org)
full5 <- stan_glm(surv ~
n_con + n_het +
BAc5*gap + BAh5*gap +
BAc5*ph + BAh5*ph +
BAc5*tec + BAh5*tec +
BAc5*org + BAh5*org,
prior = student_t(df=7, location=0, autoscale=TRUE),
prior_intercept = student_t(df=7, location=0, autoscale=TRUE),
adapt_delta = 0.99,
init_r = 0.1,
family = binomial(link = "logit"),
data = dat)
```

`l_full5 <- loo(full5, k_threshold=0.7)`

I hugely appreciate any guidance you might have. Thank you so much for the work you do!

- Operating System: Windows 10
- rstanarm Version: 2.17.4
- loo Version: 2.0.0
- R Version: 3.3.1