optimizing fails on simple example when draws > 0

Summary:

Running the simple example given in the documentation for rstan::optimizing, but adding a nonzero value for draws, results in an error.

Description:

The documentation for rstan::optimizing gives the following example code:

m <- stan_model(model_code = 'parameters {real y;} model {y ~ normal(0,1);}')
f <- optimizing(m, hessian = TRUE)

This runs fine, but if I add a nonzero draws parameter

m <- stan_model(model_code = 'parameters {real y;} model {y ~ normal(0,1);}')
f <- optimizing(m, hessian = TRUE, draws=10)

it fails with this error:

Error in dimnames(x) <- dn : 
  length of 'dimnames' [2] not equal to array extent

Reproducible Steps:

See above.

Current Output:

See above.

Expected Output:

Successful completion of call.

RStan Version:

2.18.1

R Version:

R version 3.4.3 (2017-11-30)

Operating System:

macOS High Sierra (version 10.13.6)

Start by running the documented rstan::optimizing example with hessian = TRUE and then with draws = 10, using the reported RStan and R versions if available. Trace the optimizing entry point and the result construction that raises the dimnames error; done means the draws example completes successfully while the original example remains working.